KR101027140B1 - Method for purifying contaminated soil/groundwater using nano-scale zero-valent iron and direct injection-permeable reactive barrier - Google Patents

Abstract

PURPOSE: A method for purifying contaminated area containing contaminated soil or underground water is provided to reduce cost required for installation using a direct injection-permeable reactive barrier based technique. CONSTITUTION: A method for purifying contaminated area using nZVI and a direct injection-permeable reactive barrier based technique. A contaminated area containing contaminated soil and underground water is classified into highly contaminated area and lowly contaminated area. An injection wall, a monitoring well, and a multi-monitoring well are installed at the contaminated areas. The nZVI is injected through the injection well. The effective radius and purifying efficiency and harmness of the contaminated areas are monitored using the monitoring well and the multi-monitoring well.

Description

Method for Purifying Contaminated Soil / Groundwater Using Nano-scale Zero-Valent Iron and Direct Injection-Permeable Reactive Barrier}

The present invention relates to a contaminated area purifying method including contaminated soil or groundwater using nZVI and Direct Injection-Permeable Reactive Barrier (DI-PRB), and more particularly, to contaminated soil or groundwater. After dividing the area into high concentration (Hot Source) and low concentration (Plume) according to the concentration of the pollutant, characterized in that by injecting nZVI directly by modeling the nZVI injection conditions according to the characteristics of the separated pollution area, It relates to a contaminated area purification method including contaminated soil or groundwater using nZVI and Direct Injection-Permeable Reactive Barrier (DI-PRB).

The use of iron in the environmental field can be divided into the following cases. As a method of utilizing iron, which has been applied to the water treatment field for the past 20 years, there are Fenton and Fenton-like oxidation using radical hydroxide generated by the reaction of divalent or zero-valent iron with hydrogen peroxide. In addition, the ZVI research is being actively commercialized, the heavy metal immobilization and desalination reaction using the oxidation / reduction reaction of iron, which has recently been commercialized.

Various materials can be used to treat pollutants by oxidation / reduction reactions as long as they have reducing power as transition metals. In particular, zero-valent metal iron (Fe ⁰ , Zero Valent Iron, ZVI) is the most widely used. Reactive metals include Ca (-2.87), Mg (-2.70), etc., and the reducing power is also higher than iron, but metal iron is relatively high in reactivity and readily available and can produce particles of desired size. have. In addition, it is inexpensive and very economical because it is possible to use recycled materials such as metal scrap. Although iron is included in heavy metals, its toxicity is so low that even a small amount of iron in groundwater does not have a significant adverse effect on humans or ecosystems.

In order to cause the dechlorination reduction reaction using the transition metal, electron transfer is required, and three models have been proposed according to the contact method of iron and contaminants. (Scherer et al . 1999). In the first model, cathode and anode domains are generated by oxidation of iron surface, and contaminants are directly contacted with cathode. Can not. Thus, the second model presented is a model in which the oxide film formed on the iron surface acts as a semi-conductor, and the reduction reaction of organic matter is carried out through the reduction potential reduced by the oxide film thickness. In this case, we can supplement the first direct contact model, but still only account for the surface response. In the third case, the model shows that the reaction can proceed by coordination of Fe-H and Fe-OH bonds in the oxide film on the iron surface. In this case, the reduction potential is the lowest.

It is reported that zero iron has a reduction potential of -0.3 to 0.7 V depending on the type thereof, and a reduction reaction having a lower potential than that of iron can be theoretically treated. Research on the removal of contaminants by using such ferric iron is ongoing. Chlorinated organic pollutants that can be treated by desalination reaction with iron are halogenated ethylenes (TCE, PCE), halogenated alkanes (TCM, DCM, etc.) and halogenated compounds. Aromatics (phenol chlorides, PCBs, dioxins, PBDEs), etc., vary in processing speed, but most of them can be desalted. Nitrogen compounds such as nitrate, nitrite, and nitro-aromatics are reduced to nitrogen gas at very fast reaction rates and can be applied to water treatment. In addition, it has been reported that heavy metals such as Cr, As, Pb, Zn, and Ni and radioactive materials such as uranium can be treated by adsorption reaction by oxidation / reduction.

Non-in-situ purification technology and in-situ purification technology are representative examples of the purification process.

Non-in situ purification technology is a technology that excavates and moves contaminated soils, which makes it easy to manage and evaluate the treatment process, but it requires a lot of costs for excavation and movement, and causes disturbance of ground environment in the excavation process. There is a possibility. In-situ technology, on the other hand, is a technology that directly handles contaminated soils on site, and it is less likely to expose pollutants to the surrounding environment and is less expensive than non-in situ technologies. However, in situ soil inhomogeneities can limit purification efficiency, requiring careful site assessment and monitoring techniques.

 These techniques can be classified into biological, physicochemical, and thermal techniques, depending on how the source is removed. Thermal treatment technology is a technology that decomposes harmful substances contained in soil through heat treatment (incineration) by direct combustion and heat treatment (pyrolysis) by indirect combustion by exposing soil to high temperature. However, it has the advantage of having a high purification efficiency and a wide range of applications, high energy processing costs, heavy metals are not treated at a certain temperature and has the disadvantage of vitrification at high temperatures.

Physical and chemical treatment techniques include extraction using solvents such as water, acids, organic solvents, and surfactants or steam, or by transferring the pollutants from soil and groundwater to other media by electrical methods, or by chemical oxidation / reduction methods. There is a method of separating and concentration separately through the method, adsorption / precipitation. Solidification and stabilization techniques should consider the physical and chemical properties of the heavy metals and the hardeners / stabilizers as a way of physically confining the contaminants or reducing their mobility by chemical reactions between additives and contaminants.

Biological treatment technology is a method that promotes biodegradation of organic compounds by activating or optimizing soil microorganisms or by adding specially developed microorganisms and optimizing survival conditions, which is more environmentally friendly and economical than other technologies. In recent years, the development of microbial strains capable of decomposing each contaminant and the identification of its degradation mechanism have been made, and the speed of development is increasing. However, the restoration period is long, the efficiency is limited in the high concentration of toxic contaminants and there is a disadvantage that is sensitive to changes in environmental conditions.

In general, when the concentration of pollutants is high and the size of the polluted area is small, thermal treatment is used, and when the concentration of the pollutant is low and the size of the polluted area is large, biological treatment is considered to be advantageous.

Among these techniques, recently used permeable reactive barriers (PRBs) were used as methods for applying them to the site using oxidation / reduction of reactive materials (FIG. 1). It proceeds through drilling, casing installation, reaction material laying, casing drawing, and it is possible to adjust the casing installation depth and installation depth according to geological conditions. The main treatment targets groundwater. PRB installs a reactive medium that is similar in permeability to the soil in a direction perpendicular to the flow of groundwater in the soil, so that the pollutant reacts while the groundwater containing the pollutant passes through the reactive material. This technique allows for in situ treatment of groundwater and soil in the sense that energy input is unnecessary and the process is simple. In recent decades, the technology has been used to treat groundwater and soil pollution in the United States, Korea and Sweden.

However, the existing method requires excavation to inject the reactant into the basement, so the construction cost is high, and if the reactant decreases, the reconstruction is necessary. Also, it is sufficient to induce the groundwater flow to the reaction wall. In order to secure permeability, an additional medium is required, and when the contaminants are precipitated in the wall, the permeability is lowered and there is a concern that the contaminants may be diffused. And in a wide area, it is necessary to install barriers to prevent the contaminated groundwater from flowing in the other direction. For this purpose, the installation of barriers directly increases the construction cost. Therefore, there is a problem that the reaction wall technology is applied to a limited area, such as a narrow area or a landfill and mine drainage in the existing.

Accordingly, the present inventors have made efforts to solve the problems of the prior art, and after installing the wells in the contaminated area, the nanophenols (Polyphenol-coated Nano Zero Valent Iron, P-nZVI) coated with natural polyphenols are used. By directly injecting through the well, it was confirmed that the contaminated area can be purified by a simple method without an excavation process, and the purification efficiency can be improved due to the use of P-nZVI.

An object of the present invention is to provide a contaminated soil and ground water purification method using nZVI and Direct Injection-Permeable Reactive Barrier (DI-PRB).

In order to achieve the above object, (a) dividing the contaminated area including the contaminated soil or groundwater into a high concentration pollution (Hot Source) and a low concentration pollution (Plume); (b) installing an injection well (IW), a monitoring well (MW) and a multi-monitoring well (M-MW) in the high concentration or low concentration contamination area; (c) injecting nZVI through the IW; And (d) monitoring the radius of influence, purification efficiency, and risk of the high concentration or low concentration contamination area using the MW and M-MW, Direct Injection-Permeable Reactive. Barrier, DI-PRB) provides contaminated soil and groundwater purification.

According to the present invention, it is possible to reduce the construction cost by using the direct injection method without digging when cleaning the contaminated area, to treat the contaminated area where in-situ treatment was not possible, and contaminants due to the use of nano-iron. High efficiency can be expected in the purification.

In accordance with one aspect of the present invention, there is provided a method comprising: (a) dividing a contaminated area including contaminated soil or groundwater into a high concentration contaminated area (Hot Source) and a low concentration contaminated area (Plume); (b) installing an injection well (IW), a monitoring well (MW) and a multi-monitoring well (M-MW) in the high concentration or low concentration contamination area; (c) injecting nZVI through the IW; And (d) monitoring the radius of influence, purification efficiency, and risk of the high concentration or low concentration contamination area using the MW and M-MW, Direct Injection-Permeable Reactive. Barrier, DI-PRB) relates to a contaminated soil and groundwater purification method (Fig. 2).

The present invention is purified by injecting a purifying agent in the contaminated area, characterized in that the injection directly to the WELL base using nZVI as a purifying agent.

As used herein, the term "Direct Injection-Permeable Reactive Barrier (DI-PRB)" directly injects a purifying agent, nZVI, into a contaminated area, such as soil or groundwater, so that the injected nZVI is the same as the PRB. It means a method to form a form, that is, a concept that is distinct from the method of installing a general PRB through excavation in a contaminated area.

As used herein, the term "effect radius" refers to the area where nZVI can migrate to purify the contaminated area.

The term "rebound" as used herein refers to the reoccurrence of contaminants removed by the purification process of the present invention.

As used herein, the term “nZVI” refers to nanoferrous iron commonly used.

As used herein, the term "P-nZVI" refers to nano-ferrous iron coated with Polyphenol.

As used herein, the term "Fe-containing solution" means a solution in which Fe is ionized and contained. For example, Fe may be FeCl ₃ · 6H ₂ O aqueous solution containing Fe ^{3+ in} the state.

As used herein, the term "polyphenol-Fe solution" refers to a solution in which the Fe-containing solution and Polyphenol are mixed.

In the present invention, nZVI may be characterized as P-nZVI containing Fe ⁰ and coated with Polyphenol. The content of Fe ⁰ in the P-nZVI is 42 to 50% by weight, the thickness of the coated polyphenol is 3 to 5nm, the particle size of the P-nZVI may be 40 ~ 80nm. The P-nZVI is contaminated including a material selected from the group consisting of heavy metals, nitrates (NO ^3- ), sulfates (SO ^4- ), organic halogen contaminants, DNA Non-Aqeous Phase Liquid (DNAPL) and mixtures thereof It is used for purification of materials, and heavy metals jegeoryeok is ^{0.1 ~ 0.2g Cr 6+ / g Fe} 0 on the basis of Cr ^6+.

In the purification method according to the present invention, first, after conducting a site survey for a contaminated area including contaminated soil or groundwater, it is classified into a high concentration contaminated area and a low concentration contaminated area.

In the field survey, basic analysis items include soil matric, soil porosity, permeability, groundwater gradient and velocity, and depth to water table. , Groundwater characterization [pH, ionic strength, DO (Dissolved oxygen) and Oxidation-Redcution Potential (ORP), nitrate], nitrite and sulfate Ionic and natural organic matter.

 In the present invention, the high concentration of the contaminated area is TCE concentration of 0.5ppm or more, the low concentration of the contaminated area may be characterized in that the TCE concentration is less than 0.5ppm. The high concentration contaminated area may be referred to as a hot source where TCE was first leaked, and the low concentration area may mean an area gradually expanded / diluted from the hot source area to the rear end in the flow direction of the groundwater.

Identify the location, form, and distribution of pollutants in high concentration or hot concentration pollutants, and then model the conditions of the purification process, and then use well modeled IW and MW. NZVI is injected through the IW, and the contaminated area is monitored using the MW.

In the high concentration of contaminated area, since pollutants are distributed at high concentration in a narrow range, it is preferable to install IW densely and inject high concentration of nZVI. Detailed well installation conditions and nZVI injection conditions of the high concentration of the contaminated area are shown in Table 1 (FIG. 3).

 Well installation and injection condition in high concentration contaminated area Contents Condition Contents Condition IW installation interval 1-3m Multi-MW Not installed IW installation depth To bedrock GW-Circulation use TCE concentration (mg / L) 0.5 or more Radius of influence 2-3m nZVI injection concentration (g / L) 10-50g / L Processing period 2-3 months nZVI additional injection Injection when rebound occurs nZVI / TCE (g / g) 200-300

Since contaminants are widely spread in the low concentration contaminated area, it is preferable to install IW over a wide range to inject a low concentration of nZVI so that the influence radius can be sufficiently secured by using the excellent mobility and reactivity of the injected nZVI. desirable. Detailed well installation conditions and nZVI injection conditions of the low concentration contaminated area are shown in Table 2 (FIG. 4).

 Well installation and injection condition in low concentration contaminated area Contents Condition Contents Condition IW installation interval 5 ~ 10m Multi-MW Not installed IW installation depth To bedrock GW-Circulation use TCE concentration (mg / L) 0.5 or less Radius of influence 5 ~ 10m nZVI injection concentration (g / L) 0.1 ~ 10g / L Processing period 2-3 months nZVI additional injection Injection when rebound occurs nZVI / TCE (g / g) 400-600

In the present invention, the conditions of the purification method may be selected from the group consisting of the installation interval of the IW and MW, the installation position of the IW and MW, the type of nZVI, the injection concentration of nZVI and the injection amount of nZVI.

In the present invention, the IW may be installed at intervals of 2 to 3 m in the high concentration pollution area, and the IW may be installed at intervals of 5 to 10 m in the low concentration pollution area.

In the present invention, the MW may be installed at the front and rear ends of the IW at intervals of 5 to 10 m, respectively, in order to monitor the purification efficiency of the pollutant. For example, if IW is installed in a contaminated area containing contaminated groundwater, and installed at the front and rear ends of the IW, the groundwater flows continuously and continuously monitors the movement and reduction of pollutant sources before nZVI is injected through the IW. (FIG. 5).

In the present invention, the injection amount of the nZVI in the high concentration contaminated area is 20000 to 30000 parts by weight based on 100 parts by weight of TCE, the injection amount of the nZVI in the low concentration contaminated area is 40000 to 60000 parts by weight based on 100 parts by weight of TCE It can be characterized. After the nZVI injection amount is determined according to the different TCE content according to the high concentration and low concentration pollution area, the injection efficiency can be maximized by direct injection.

In the present invention, the implant is nZVI permeability of the contaminated soil ^{(k, x10 -4 cm / sec} ) is 500 to 5000 is directly injected, and the permeability of the contaminated soil (k, x10 ^-4 cm / sec of In soils with 0.01 ~ 20), soil fracturing is carried out to ensure permeability, and then nZVI is injected directly, and when the surface is contaminated from the contaminated soil or taken out and cleaned, the nZVI is applied to the soil. And it may be characterized by being carried out by stirring.

In other words, when the contaminated area includes soil, the nZVI can be injected in different ways depending on the permeability coefficient of the contaminated soil.

If the permeability of the contaminated soil (k, x10 ^-4 cm / sec) is good permeability of more than 500 or less than 5000, nZVI is directly injected because nZVI is excellent in purifying efficiency even when directly injecting the contaminated soil.

If the permeability coefficient (k, x10 ^-4 cm / sec) of contaminated soil has a permeability of 20 or more and about 499, nZVI is directly injected into the contaminated soil, nZVI is applied after fracturing the soil. Combine the method of direct injection.

If the permeability coefficient (k, x10 ^-4 cm / sec) of the contaminated soil is not good permeability of about 0.01 to 20, it is preferable to increase the purification efficiency by injecting nZVI directly after fracturing the soil. Here, the Fracturing of the air fracture (Pneumatic Fracturing), hydraulic fracturing (Hydraulic Fracutring) and blast fracture (Blast Fracutring).

If the surface of the contaminated soil is contaminated or is purged by ex-intu, such as using an external purification treatment facility, nZVI is applied to the contaminated soil and then purified by mixing the contaminated soil. You can do

After the application of purification methods to the contaminated area, well installation and nZVI injection, the contaminated area is monitored using MW.

Items to be monitored after injecting nZVI are DO, pH, ORP and contaminant concentrations. After nZVI injection, DO decreases due to the reaction of nZVI with oxygen, pH increases due to H ₂ production, ORP decreases, and contaminant concentrations decrease due to the purification of nZVI. For example, when the purification method according to the present invention is applied to groundwater, the DO is lower than the groundwater DO concentration (5 ~ 6mg / L), the pH is increased to 1 to 3 by H ₂ generation, ORP is It is about 400 ~ 500mV, but after injection, it decreases to -400 ~ 700mV. Contaminants can be seen to decrease within a few days. However, over time, the reactivity of nZVI decreases, resulting in changes in DO, pH, ORP and contaminant concentrations. In particular, when the ORP value gradually increases, reinjection of contaminants (TCE) occurs, so re-injection of nano-ferrous iron should be considered. As such, the concentration of DO, pH, ORP and contaminants, as well as the direction of movement of the contaminants may be continuously monitored to determine whether to apply the purification method.

In the present invention, the purification method may be characterized by purifying contaminated soil and groundwater by dechlorination of organic chlorine pollutants, precipitation of heavy metals and reduction of nitrates and sulfates.

In the present invention, the P-nZVI may be characterized by containing Fe ⁰ coated with polyphenol (polyphenol).

The P-nZVI may be prepared by adding polyphenol, which is a natural substance, in the process of preparing nano-iron iron by a wet reduction method, which is a synthetic method using a reducing agent. Polyphenol (hydrolyzable tannis) is a natural substance having two or more hydroxyl groups, also called a polyhydric phenol, and the nano-ferrous iron coated with polyphenol according to the present invention exhibits excellent reaction stability, dispersibility, and mobility due to the polyphenol coating film. It will not cause secondary pollution.

The P-nZVI may be prepared by adding polyphenol, which is a natural substance, in the process of preparing nano-iron iron by a wet reduction method, which is a synthetic method using a reducing agent. Specifically, (a) adding a polyphenol to the Fe-containing solution to prepare a Polyphenol-Fe solution; And (b) adding a reducing agent to the polyphenol-Fe solution to obtain a synthesized P-nZVI.

According to the present invention, since the nZVI is directly injected into the contaminated area through the well, which improves reactivity, dispersibility, and mobility as a purifier, no additional excavation is required, and the soil is combined with basic business activities and performances in industrial complexes and military units. To clean up contaminated areas, including groundwater and groundwater. In addition, by conducting a site survey on the contaminated area, depending on the concentration of the contaminated area, and in the case of contaminated soil, the injection efficiency of nZVI can be improved by changing the method of injecting nZVI according to the permeability of the soil.

Hereinafter, the present invention will be described in more detail by way of examples. These examples are intended to illustrate the present invention in more detail, and it will be apparent to those skilled in the art that the scope of the present invention is not limited to these examples.

In particular, in the present embodiment, P-nZVI was used as a purifier for purifying soil or ground water, but it is obvious to those skilled in the art that the present invention is not limited thereto.

Example 1 Preparation of P-nZVI

Reagents used to prepare P-nZVI include FeCl ₃ .6H ₂ O (Aldrich Chemical, USA) for preparing Fe-containing solutions, Tannic acid (Aldrich Chemical, USA) as polyphenol and NaBH ₄ (Aldrich Chemical, USA). In addition, secondary distilled water was used as distilled water, but secondary distilled water having 0 <DO concentration <0.3 mg / L was purged with N ₂ . The following steps 1-1 and 1-2 were all purged with N ₂ and carried out in an anaerobic state.

1-1. Polyphenol-Fe Solution Preparation

13.52 g of FeCl ₃ · 6H ₂ O was dissolved in 100 ml of distilled water to prepare a 0.5 M Fe ³⁺ solution. Polyphenol-Fe aqueous solution was prepared by adding 0.46 g of tannic acid to 100 ml of the 0.5 M Fe ³⁺ solution.

1-2. Reducing agent added

0.9 g of NaBH ₄ was dissolved in 30 ml of distilled water to prepare a 0.8 M NaBH ₄ solution. The solution was added dropwise to 10 ml of an aqueous polyphenol-Fe solution prepared in 1-1, and added dropwise while appropriately changing at a rate of 0.1 to 0.6 ml / min. -nZVI was prepared (see Scheme (1)).

4Fe ³⁺ + 3BH ^4- + 9H ₂ O-> 4Fe0 + 3H ₂ BO ^3- + 12H ⁺ + 6H ₂ (1)

1-3. Ultrasonic Drying and Washing

After ultrasonication was applied to P-nZVI prepared in 1-2 for 20 minutes to dry, and then washed three times with distilled water purged with N ₂ to remove B (Boron) and impurities remaining on the surface (Fig. 9).

Example 2: P-nZVI Particle Characterization

The properties of P-nZVI prepared in Example 1 were analyzed.

2-1. Size and Shape of P-nZVI Particles

Transmission electron microscopy (TEM) (JEM-2100F, JEOL, USA) was used to analyze the size and shape of the P-nZVI particles.

As a result, as shown in Figure 10 (a), it was confirmed that the P-nZVI particles have a size of 40 ~ 80nm in average diameter.

In addition, as shown in (b) of FIG. 10, the P-nZVI particles were confirmed to have a polyphenol film having a thickness of 5 nm formed on the surface thereof to have a coated shape.

2-2. P-nZVI Component Analysis

X-ray diffraction (XRD) analysis (Max-2500V, RIGAKU, JP) confirmed that the major component of P-nZVI was Fe ⁰ .

The content of Fe ⁰ contained in P-nZVI was quantified using the H ₂ value quantified by GC-TCD (Thermal Conductivity Detector, HP-6890, USA). The amount of Fe ⁰ was quantified by quantifying H ₂ generated after (37%) injection.

As a result of quantification, it was confirmed that the Fe ⁰ content contained in P-nZVI was 47.3%. Since the Fe ⁰ content in the existing nZVI is 51.29% (Yueqiang Liu and Gregory V. Lowry., Environ. Sci. Technol. 39: 1338-1345, 2005), the Fe ⁰ content in the P-nZVI and nZVI Could see no big difference.

Fe ⁰ + 2H ⁺ -> Fe ²⁺ + H ₂ ↑ (2)

2-3. P-nZVI Specific Surface Area Measurement

BET analysis of P-nZVI was performed using ASAP 2010 Analyzer BET (Micromeritics, USA). As a result, it was confirmed that the average specific surface area (SSA) value was about 17.27 m ² / g. The reason why the specific surface area of P-nZVI was measured was that the surface area of Ni-P-NZVI was lowered due to lower Soil-Gas attractivity between Nitrogen gas and adsorbent (P-nZVI). have.

Example 3 Groundwater Purification using P-nZVI and DI-PRB

3-1: Field Survey

The groundwater flow in the polluted area was confirmed from the source of the pollutant to the industrial complex area, and the main flow direction of the groundwater was in the northeast direction, and the groundwater level was about 6.5m. Hydrogen ion concentration in groundwater of contaminated area was shown to be within the range of hydrogen ion concentration in general groundwater. Electrical conductivity was 118 ~ 1,243μS / cm and averaged 468μS / cm. Dissolved oxygen levels (3.3-4.8 mg / L), redox potentials (200-210 mV, 400-600 mV) and pH (4.8-6.5) showed an oxidative environment that was characteristic of shallow groundwater. Dissolved iron ions up to 12 mg / L (average 1.08 mg / L) and dissolved manganese ions up to 2.48 mg / L (average 0.403 mg / L). TCE contamination levels in contaminated areas were measured up to 6 mg / L at the time of initial contamination, but have recently been measured at up to 2 mg / L. From the measured TCE contamination change, it shows that the pollutant is more widely spread. In practice, the TCE concentration was 0.4 mg / L in the literature, but 1.6 mg / L in the analysis results.

The total test area was 10m * 10m * 12m and the low concentration polluted area (Plume area) was selected.

The site survey was conducted with the following equipment. Water level indicator (MODEL Waterra HS-1), DO, pH and ORP were analyzed using Orion Star 3, a portable measuring device. Contaminants PCE (perchloro-ethylene), TCE (trichloroethylene), DCE (1,2-dichloroetylene) analysis were analyzed using GC-ECD (Agilent, USA), heavy metals AA (atomic absorption, Varian, USA) The analysis was performed using.

Status of Contaminated Area MW-21 Well Property location Groundwater level (m) pH
(mg / L) EC
(mg / L) DO
(mg / L) ORP
(mg / L) Temp
(mg / L) PCE
(mg / L) TCE
(mg / L) DCE
(mg / L) MW 6.55 6.49 364.00 4.83 210.00 15.00 0.0 0.6 to 1.6 0.0 Total well 4.80 6.47 503.54 3.03 202.22 15.41 0.0 01. ~ 2.0 0.0

3-2: Modeling of Purification Condition

According to the result of targeting the Plume area in 3-1, the purification process conditions to be applied to the Plume area were modeled. In this example, a plurality of wells were identified by numbers such as IW1, IW2, MW21, and the like.

3-3: well installation

Well was drilled using geo-prove, well wall size was 50mm, 1.5m length well was connected and installed up to 12m underground, and well screen was installed from below 6.5m below ground level for nZVI injection and groundwater monitoring. Made it possible. After the well installation, the outer wall of the well was injected with silica sand to secure the permeability sufficiently, and the final upper part was fixed with cement.

Two IWs for injecting nZVI were installed (IW1 and IW2), and the groundwater and pollutant inflows were continuously monitored using the existing MW (MW12 and MW21) in front of IW based on groundwater flow, and MW at the back. 5 (MW1, MW2, MW3, MW4 and MW5) were additionally installed at intervals of 3-6 m each in the direction of the groundwater flow.

3-4: nZVI injection

In order to inject nZVI, the amount of TCE contamination in the contaminated area was calculated and nZVI was prepared. The total amount of TCE in the contaminated area was estimated to be 43.68g, which required 3.37kg of nZVI, and a total of 11kg of nZVI was prepared by applying a safety factor of 3.0 times.

Fe ⁰ / Soil ratio was 0.001 ~ 0.00001, nZVI concentration was 0.0025kg / L was injected into the contaminated area through the IW.

 11 kg of nZVI was injected twice, and 2.5 kg was injected in the first injection to quickly determine the point of rebound of the pollutant, and 8.5 kg was injected in the second injection after confirming the rebound.

Contaminated area characteristics and nZVI injection conditions Characteristic of Field Test Site Parameter Estimates Units Length 6.5 m Width 4 m Area 26 m ² Depth 6 m Total Vol. 156 m ³ Porosity 35 % Plume Total Pore Vol. 54.6 m ³ Avg. Contaminant Conc. One ppm (mg / L) Mass of Contaminant in G.W 43.68 g nZVI Demand in Field nZVI in Slurry 0.0025 kg / L Soil mass 134.862 t F ⁰ / Soil ratio 0.001-0.00001
(0.000025) nZVI 3.37155 kg Confidence Factor 3.0 nZVI Demand 10.115 kg Injection nZVI 11 kg F ⁰ / TCE ratio 232/252

3-5: monitoring

Monitoring was performed for about 4 months after nZVI infusion.

As a result, as shown in Figure 6, after the first injection was confirmed about 1 month after the TCE rebound phenomenon, after the second injection was confirmed that gradually rebound after about 3 months. At the initial TCE concentration of 0.6-1.6mg / L, after nZVI injection, it decreased to about 0.01 ~ 0.03mg / L, and the total removal rate of TCE was about 85%.

 After nZVI injection, the pH gradually increased to an initial pH of 6.0, up to 9.0 after injection, and DO decreased from an initial 5.6 to 8.0 mg / L up to 0.5 mg / L after nZVI injection. In addition, as shown in Figure 7, ORP was 400mV at the beginning before injection, but after the nZVI injection reduced to -400 ~ -500mV to create a strong reducing atmosphere.

 The radius of influence increased from pH 6.0 to pH 7.5 even in the farthest MW 5, DO value decreased from 7.2 mg / L up to 1.0 g / L, and ORP decreased from 350 mV up to about -400 mV. It was. Based on this, the impact radius was confirmed to be at least about 5m or more, and it was also seen that nZVI flowed out to the ground about 12m away to secure an influence radius up to 12m (Fig. 8).

While the present invention has been particularly shown and described with reference to specific embodiments thereof, those skilled in the art will appreciate that such specific embodiments are merely preferred embodiments and that the scope of the present invention is not limited thereby. something to do. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

1 is a diagram of permeable reactive barriers (PRBs) drilled in a contaminated area.

2 is a flow chart of the purification method according to the present invention.

Figure 3 shows a high concentration of contaminated area according to the present invention.

Figure 3 shows a low concentration of contaminated area according to the present invention.

5 is a position (W) WELL is installed in the pollution area subject to the purification method according to the present invention; And injecting nZVI ((b) and (c)).

6 is a graph showing the change in TCE concentration after nZVI injection into the contaminated area.

7 is a graph showing the change in ORP after nZVI injection in the contaminated area.

8 is a schematic diagram of a contaminated area purification method including contaminated soil or groundwater using nZVI and DI-PRB.

9 is a manufacturing process diagram of P-nZVI according to the present invention.

10 is a TEM photograph of P-nZVI according to the present invention.

Claims (9)

Purification of contaminated soil or groundwater using Nano-Scale Zero-Valent Iron (nZVI) and Direct Injection-Permeable Reactive Barrier (DI-PRB), including the following steps: (a) dividing the contaminated area including contaminated soil or groundwater into a hot source and a low concentration pollution; (b) installing an injection well (IW), a monitoring well (MW) and a multi-monitoring well (M-MW) in the high concentration or low concentration contamination area; (c) injecting nZVI through the IW; And (d) monitoring the impact radius, purification efficiency and risk of the high concentration or low concentration contamination area using the MW and M-MW. The method of claim 1, wherein the nano-scale zero-valent iron (nZVI) is polyphenol-coated nano zero-valent iron (P-nZVI) containing Fe ⁰ and coated with polyphenol. The method of claim 1, wherein the high concentration contaminated area has a TCE (Trichloroethylene) concentration of 0.5 ppm or more, and the low concentration contaminated area has a TCE (Trichloroethylene) concentration of less than 0.5 ppm. The method according to claim 1, wherein the purification method adjusts conditions selected from the group consisting of IW and MW installation intervals, IW and MW installation positions, and nZVI injection concentrations. The method according to claim 1, wherein the IW is installed at intervals of 2 to 3 m in the high concentration polluted area, and the IW is installed at intervals of 5 to 10 m in the low concentration polluted area. The method according to claim 1, wherein the MW is installed at the front and rear ends of the IW at intervals of 5 to 10 m to monitor the purification efficiency of the pollutant. According to claim 1, wherein the injection amount of the nZVI in the high concentration of contaminated region is 20000 ~ 30000 parts by weight based on 100 parts by weight of TCE (trichloroethylene), The injection amount of the nZVI in the low concentration contaminated area is 40000 ~ 100 parts by weight It is 60000 parts by weight. The method of claim 1, wherein the injection of nZVI If the permeability coefficient (k, x10 ^-4 cm / sec) of the contaminated soil is 500 or less than 5000 directly injected, If the permeability coefficient of the contaminated soil (k, x10 ^-4 cm / sec) is 20 or more and less than 499, the direct injection and the direct injection after the soil fracturing (fracturing) is injected in parallel, In a soil having a permeability coefficient (k, x10 ^-4 cm / sec) of 0.01 to 20 of the contaminated soil, the method is characterized in that the nZVI is injected directly after the soil crushing (fracturing) to secure the permeability. The method according to claim 1, wherein the contaminated soil and groundwater are purified by desalination of the organic halogen contaminants with the injected nZVI, precipitation of heavy metals, and reduction of nitrates and sulfates.

Images