KR20120038793A - D-NVI attached to the surface of iron sulfide sediment and method for purifying polluted soil and groundwater environmental pollutants - Google Patents

Abstract

PURPOSE: Dithionite-mediated nanoscale zerovalent iron(D-nZVI) with ferrous sulfide precipitate on the surface and a method for purifying polluted soil and underground environmental pollutants using the same are provided to synthesize nanoscale zerovalent iron by adding dithionite to a sodium borohydride method. CONSTITUTION: Ferrous sulfide precipitate is deposited on the surface of D-nZVI. The specific surface are of the D-nZVI is larger than the specific surface are of nZVI and is between 4 and 60m^2/g. The surface roughness of the D-nZVI is between 40 and 50nm and is larger than the surface roughness of the nZVI. The electric conductivity of the D-nZVI is 6times more than the electric conductivity of the nZVI. A method for manufacturing the D-nZVI includes a process in which sodium dithionite is added into a sodium borohydride reducing agent to deposit the ferrous sulfide precipitate on the surface of nZVI.

Description

D-NVI attached to the surface of iron sulfide sediment and method for purifying polluted soil and groundwater environmental pollutants using the same

The present invention relates to Nanoscale Zero Valent Iron (NZVI) for the purification of organic pollutants and heavy metals in soil / groundwater, and more particularly, the reducing agent itself is a reducing agent and various sulfur in the conventional method using Sodium Borohydride. The present invention relates to nano-ferrous iron (Dithionite-mediated nZVI; D-nZVI) surface-attached with a ferrous sulfide precipitate by adding Dithionite as a source of a substance, and a method for purifying environmental pollutants using the same. The D-nZVI is applied to desalination and immobilization of organic pollutants such as trichloroethylene (TCE) in soil and groundwater and environmental pollutants such as heavy metals.

Nano-sized iron particles are the fields of most interest to environmental scientists and engineers because of their various applications besides the removal of environmental pollutants. As nanotechnology is developed, there are many applications of nZVI for the treatment of organic pollutants in soil / groundwater. It is getting attention.

First of all, the mechanism of removing chlorinated organic matter by iron ions is as follows. Iron (Fe ⁰ ), which is present as iron, is oxidized and forms a redox couple. This is similar to the corrosion reaction caused by spontaneous oxidation due to the tendency of the noble metal to lose electrons and to exist in cation form.

Fe ⁰ ↔ Fe ^{2 + +} 2e ^-

That is, the main reducing agent that can react with the organic chloride compound is Fe ⁰ , Fe ^{2 +} ,. In the case of the corrosion reaction and the like dechlorination operation by the dechlorination of the Fe ^{2 +} is a yiruna predominantly, in addition to generating the corrosion reaction by direct electron exchange with the alkyl chloride adsorbed to the surface from Fe ^0. The desalination process of alkyl halides (RXs) by these iron reducing agents can be expressed as follows.

^{Fe 0 + RX + H + ↔} Fe 2 + + RH + X -

^{2Fe 2 + + RX + H +} ↔ 2Fe 3 + + RH + X -

In addition, among various transition metals, iron has a relatively high reducing power (-0.3 to -0.7 V) and is most widely used because it is inexpensive and easy to obtain. In order for dechlorination and reduction reactions to occur due to zero iron, the adsorption of pollutants to the iron surface and the electron transfer reaction must be organically linked. Electron transfer reaction is known to transfer electrons from defects on the surface of iron directly or indirectly by coordination of Fe-H and Fe-OH bonds in oxide or oxide film that acts as a semi-conductor. . As a result, the reduction reaction of contaminants through the surface of zero iron is affected by the shape and characteristics of the surface of zero iron.

In particular, nZVI is a halogen organic solvent such as trichloroethylene (TCE), tetrachloroethylene (PCE) due to the high reactivity due to the large specific surface area; Halogen aromatic substances such as phenol chloride, Polychlorinated Biphenyl (PCBs), Polychlorinated Dibenzodioxins (PCDDs), and Polybrominated diphenyl ethers (PBDEs); Heavy metals such as chromium, lead and arsenic; nitrate; Herbicides; Polycyclic aromatic hydrocarbons (PAH); Trichloroethane (TCA); Tetrachloroethane (PCA); chloroform; Nitrobenzene; Nitrotoluene; Dinitrobenzene; Dinitrotoluene; It is known to be very effective for a wide variety of transformation and detoxification reactions by oxidation / reduction treatment of environmental pollutants such as chlorinated methane.

Since the reduction reactivity of the particles themselves may vary greatly depending on the synthesis method or conditions, such a study has been continuously conducted on a new synthesis method for improving the reactivity.

On the other hand, a variety of minerals are found around the permeable reactive barriers (PRBs) or injection wells that are caused by the oxidation of ferrous iron such as iron oxides, iron carbonates and iron sulfides. As the removal of contaminants has been reported continuously after the complete oxidation of the ferrous iron around the reaction wall, the reduction ability of the mineral substances in the form of sediment on the iron surface is receiving much attention. Among these, iron sulfide (FeS _x ) produced by hydrogen sulfide produced by Sulfur Reducing Bacteria (SRB) under anaerobic reaction with iron ions is known to have higher reactivity per unit area than iron in the literature ( Butler, EC et al ., Environ . Sci . Technol . , 35: 3884-3891, 2001).

In particular, iron sulfides have different reactivity and solubility depending on the crystal structure, and the nearer the amorphous structure, the more efficient the treatment of halogen pollutants (He, YT et al ., Environ . Sci . Technol . , 42: 6690-). 6696, 2008). Therefore, making nanoparticles with covalent iron and ferrous sulfide materials would be a useful way to improve the overall degradation capacity.

As such, in view of making nanoparticles in which both ferrous iron and ferrous sulfide materials are present, sodium dithionite is a powerful and inexpensive reducing agent in itself and is widely used in the dye industry. Dithionite is unstable in aqueous solution and quickly decomposes. However, since various sulfur-containing compounds are produced according to reaction conditions such as pH, temperature and oxygen concentration, there is a difference in the exact decomposition mechanism.

When Dithionite is treated in soil, it has been reported that the removal of contaminants, including heavy metals, by itself and by its ability to reduce decomposition byproducts (Ludwig, RD et al ., Environ . Sci . Technol . , 41: 5299) -5305, 2007). For example, one of the decomposition by-products of Dithionite, Sulfoxyl radical, can convert iron (III) oxide in the environment into a highly reactive divalent compound (see Schemes (1) and (2)).

_{^{S 2 O 4 2 - → 2SO}} 2 - (1)

_{^{SO 2 - + Fe 3 + +}} H 2 O → Fe 2 + + SO 3 - + 2H + (2)

In the present invention, dithionite was added to supply sulfide ions by the following reaction in the synthesis of nZVI (De Carvalho, LM et al ., Anal . Chim. Acta . , 436: 293-300, 2001).

_{^{2S 2 O 4 2 - + H}} 2 O → 2HSO 3 - + S 2 O 3 2 - (3)

_{^{S 2 O 4 2 - + S}} 2 O 3 2 - + 2H 2 O + H + → H 2 S + 2HSO 3 - (4)

The present inventors synthesized a nanoitemium (Dithionite-mediated Nanoscale ZeroValent Iron, D-nZVI) surface-attached to the surface with a ferrous sulfide through the development of a simple synthesis method to add Dithionite to the conventional synthesis method. Through this, the surface roughness and the electrical conductivity were increased to improve the initial contact rate of pollutants and the electron transfer on the iron surface. As a result of testing the decomposition efficiency of TCE, one of the representative organic pollutants, it was confirmed that the reactivity is significantly improved compared to the conventional synthesized nZVI, and completed the present invention.

The present invention aims to solve the synthesis of new nano-ferrous iron with improved reactivity through the development of a synthetic method of adding dithionite to the borohydride method, which is a conventional method for synthesizing nano-iron iron.

In order to solve the above problems, the present invention is to prepare a D-nZVI surface-attached Ferrous sulfide precipitate as a means of solving the problem.

In addition, the specific surface area of the D-nZVI surface-attached with the ferrous sulfide precipitate is 40 ~ 60 m ² / g and larger than the specific surface area of the conventional nZVI 20 ~ 30 m ² / g as a solution to the problem.

In addition, the surface roughness value (Rrms) of D-nZVI surface-attached with the ferrous sulfide precipitate is 40 ~ 50nm and larger than the surface roughness value (Rrms) 20-30nm of conventional nZVI as a means of solving the problem.

In addition, the electrical conductivity of D-nZVI surface-attached with the ferrous sulfide precipitate is 6 times larger than the conventional nZVI as a means of solving the problem.

The invention also nano zero-valent iron synthetic process by addition of Dithionite hydrogen sulphide ions (HS ^-) in the nano-zero-valent iron Synthesis of Sodium borohydride way of the D-nZVI production method Ferrous sulfide precipitate attached to the surface by feeding challenge It is a solution.

In addition, the concentration of Dithionite in the production method is adjusted to 0.1 g / L ~ 5.0 g / L D-nZVI production method is attached to the ferrous sulfide precipitate on the surface to solve the problem.

In addition, the present invention provides a method for purifying polluted soil and groundwater environmental pollutants, including reducing the environmental pollutants with D-nZVI on which the ferrous sulfide precipitates are attached to the surface.

In addition, the environmental pollutants include a trichloroethylene (TCE), a halogen organic solvent of tetrachloroethylene (TCE); Halogen aromatics such as phenol chloride, Polychlorinated Biphenyl (PCBs), Polychlorinated Dibenzodioxins (PCDDs), and Polybrominated diphenyl ethers (PBDEs); Heavy metals of chromium, lead, arsenic, nickel; Nitrate (NO3 ^-); Sulfate (SO 4 ^-2 ); Polycyclic aromatic hydrocarbons (PAH); Trichloroethane (TCA); Tetrachloroethane (PCA); chloroform; Nitrobenzene; Nitrotoluene; Dinitrobenzene; Dinitrotoluene; Chlorinated methane is the solution to the problem.

According to the present invention, it is possible to synthesize D-nZVI, a new nano-ferrous iron with a ferrous sulfide precipitate attached to the surface, in a simple manner, which is known in the literature for the purification of organic pollutants such as TCE and environmental pollutants such as heavy metals. In comparison with nZVI reported, there is a dramatic effect of up to 16 times better processing efficiency.

1 is a manufacturing process diagram of D-nZVI according to the present invention
2 is a SEM analysis result of D-nZVI according to the present invention
Figure 3 XRD analysis of D-nZVI according to the present invention
4 is XPS analysis results of D-nZVI and nZVI according to the present invention (a: nZVI, b: D-nZVI)
5 is an AFM image of D-nZVI and nZVI according to the present invention (a: nZVI, b: D-nZVI)
6 is an EFM image of D-nZVI and nZVI according to the present invention (a: nZVI, b: D-nZVI)
7 is a graph comparing the degree of TCE reduction with the addition amount of dithionite
8 is a graph comparing TCE reduction of D-nZVI with nZVI and RNIP.

The present invention features D-nZVI having a surface attached with FeS (Ferrous sulfide) precipitate.

In addition, the specific surface area of the above-Ferrous sulfide precipitate the surface-mount D-nZVI is characterized by the technical construction that is greater than 40 ~ 60m ² / g in specific surface area of 20 ~ 30 m ² / g of a conventional nZVI.

In addition, the surface roughness value (Rrms) of the D-nZVI on which the ferrous sulfide precipitate is attached to the surface is 40-50 nm, which is larger than the surface roughness value (Rrms) 20-30 nm of the conventional nZVI.

In addition, the electrical conductivity of D-nZVI having the surface of the ferrous sulfide precipitate attached is 6 times larger than conventional nZVI.

The invention also nano zero-valent iron Synthesis of Sodium borohydride method nano zero-valent iron synthesis of hydrogen sulphide ions (HS ^-) in the addition of Dithionite the configuration described this Ferrous sulfide precipitate attached D-nZVI method for manufacturing a surface by supplying It is characterized by.

In addition, by adjusting the concentration of Dithionite added 0.1 g / L ~ 5.0 g / L in the above production method characterized in that the D-nZVI manufacturing method is attached to the ferrous sulfide precipitate on the surface.

In addition, the present invention is characterized by a method of purifying polluted soil and groundwater environmental pollutants, including oxidizing / reducing environmental pollutants with D-nZVI having the surface of the ferrous sulfide precipitate attached thereto.

In addition, the environmental pollutants include a trichloroethylene (TCE), a halogen organic solvent of tetrachloroethylene (TCE); Halogen aromatics such as phenol chloride, Polychlorinated Biphenyl (PCBs), Polychlorinated Dibenzodioxins (PCDDs), and Polybrominated diphenyl ethers (PBDEs); Heavy metals of chromium, lead, arsenic, nickel; Nitrate (NO3 ^-); Sulfate (SO 4 ^-2 ); Polycyclic aromatic hydrocarbons (PAH); Trichloroethane (TCA); Tetrachloroethane (PCA); chloroform; Nitrobenzene; Nitrotoluene; Dinitrobenzene; Dinitrotoluene; Chlorinated methane is characterized by a technical configuration.

Hereinafter, the present invention will be described in detail.

The term 'nZVI' as used herein, by reduction of the Fe solution without Dithionite added NaBH ₄ means a nano zero-valent iron obtained and, 'D-nZVI' nano zero-valent iron is obtained by reduction with NaBH ₄ was added to Dithionite the Fe solution Means.

In the present invention, the reduction of environmental pollutants by D-nZVI is carried out through the surface of the metal, in order to increase the reduction capacity of the nano-ferrous iron is generated by the adsorption of contaminants to the surface of the non-ferrous iron and oxidation of iron. Electron transfer reaction should be promoted.

The adsorption reaction may vary depending on the specific surface area and surface roughness. The specific surface area of D-nZVI synthesized in the present invention is 40-60 m ² / g, and the specific surface area of nano-ferrous iron reported in the literature is 20-30 m ^2. It is much larger than / g. D-nZVI can increase the initial adsorption rate due to the large specific surface area, which in turn can enable an improvement in the overall rate of reduction.

Therefore, the surface roughness of D-nZVI surface is increased by about twice that of nZVI synthesized under the same conditions without the addition of dithionite due to the precipitation of ferrous sulfide. It was confirmed by AFM (Atomic Force Microscopy) analysis that the surface roughness (Rrms) of D-nZVI is 40-50 nm, which is larger than the surface roughness (Rrms) of conventional nZVI 20-30nm. There are many edges on rough surfaces, which are known to have better adsorption of contaminants than flat surfaces (Tansel, B. et. al ., Adv . Environ . Res . , 8: 411-415, 2004). In addition, the ferrous sulfide in the aqueous solution has a tendency to hydration (hydration) less than iron oxide has a number of hydrophobic sites on the surface has the advantage that the adsorption of environmental pollutants can be further promoted.

Furthermore, as a result of Electrostatic Force Microscopy (EMF) measurement, it can be seen that the synthesized D-nZVI has at least 6 times more electrical conductivity than nZVI. This means that the movement of electrons is more active on the surface of D-nZVI. Iron sulfide is actually known to be a highly conductive material due to the presence of non-local electron pairs. Since the reduction process of pollutants is a reaction that takes place by receiving electrons from the surface of the metal, it can be seen that it is easy to transfer electrons to the environmental pollutants adsorbed on the surface of D-nZVI.

In conclusion, the reduction rate of D-nZVI's reduction of environmental pollutants can be attributed to (1) increased specific surface area, (2) increased surface roughness due to ferrous sulfide precipitation on the surface of ductile iron, and (3) increased surface conductivity. It can be seen that it is due to the increase in the adsorption and electron transfer reaction rate.

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.

Preparation of Experimental Materials

TCE (Trichloroethylene, Sigma Aldrich, USA) was prepared as an environmental pollutant. Ferric chloride (FeCl ₃ -6H ₂ O, Sigma Aldrich, USA), Sodium borohydride (NaBH ₄ , Sigma Aldrich, USA) and Sodium dithionite (Na ₂ S ₂ O ₄ , Sigma Aldrich, USA) for the preparation of nZVI and D-nZVI ) Was prepared. In order to use in the comparative experiments on the nano-ferrous iron prepared above, RNIP (Reactive Nanoscale Iron Particles, Toda Corp., Japan) was prepared. RNIP was used three times with distilled water purged with N ₂ to remove surface impurities before the reaction.

Preparation of D-nZVI

Distilled water was used as the third distilled water (18MO cm) purged with N ₂ for 1 hour, the following 2-1 and 2-2 process is all N ₂ The purge was performed.

2-1. Fe  Solution manufacturing

FeCl _3? 6H ₂ O 13.5 g to prepare a 0.5 M solution of Fe ^{+ 3} is dissolved in distilled water to 100 ml.

2-2. Reducing agent added

3.0 g of NaBH ₄ was prepared in a solution of 0.8M NaBH ₄ dissolved in 100 ml of distilled water. After adding 0.2 g of sodium dithionite to the solution to prepare an aqueous solution of sodium dithionite-NaBH ₄ , 9 ml of the solution was added dropwise to 3 ml of the Fe solution prepared in 2-1 at a rate of 1 ml / min. This produced 0.08 g of D-nZVI. (See Scheme (5))

^{_{Fe (H 2 O) 6 3+}} (aq) + 3BH 4 - + 3H 2 O → Fe 0 (s) + 3B (OH) 3 + 10.5H 2 (g) (5)

Here, in the case of preparing sodium dithionite-NaBH ₄ reductant solution by adding sodium dithionite, the synthesis cost of total nanocomposite can be reduced by adjusting the ratio of sodium dithionite and NaBH ₄ to reduce the use of expensive NaBH _{4 by the} amount of sodium dithionite added. Can be.

2-3. Ultrasonic Drying and Washing

Ultrasonic waves were added to D-nZVI prepared in 2-2 for 10 minutes, and then washed three times with distilled water purged with N ₂ to remove impurities from the surface (FIG. 1).

D-nZVI particle characterization

3-1. D- nZVI Surface shape of

The surface shape and elemental composition of the D-nZVI were analyzed using FE-SEM / EDX (Field emission scanning electron microscopy / energy dispersive X-ray) (JSM-7401F, JEOL, Japan).

As a result, as shown in (a) of FIG. 2, the D-nZVI particles can be confirmed that spherical iron particles are connected in a chain structure similarly to previously reported nZVI.

In addition, sulfur (S) signals were observed in addition to iron (Fe) and oxygen (O) in the surface EDX analysis (FIG. 2 (b)). As a result of X-ray mapping, sulfur is uniformly distributed on the iron surface. It could be confirmed (Fig. 2 (c)).

3-2. D- nZVI Component Analysis of

XRD (X-ray diffraction) (MXP18 HF, MAC science co., Japan) analysis confirmed that the main component of D-nZVI is Fe ⁰ (Fig. 3). However, no sulfur-containing compound was found, which was determined by the XRD analysis of the crystal structure of the material that the sulfur compound present in D-nZVI would have an amorphous structure.

3-3. D- nZVI  Surface characterization

An x-ray photoelectron spectroscopy (XPS) analyzer using an Mg Ka (1253.6 eV) line (ESCA Lab 220iXL, VG scientific, USA) was used to measure the chemical composition of Sulfur and the chemical composition of D-nZVI. .

As shown in Table 1, when compared with the composition ratios of Fe, S, and B of nZVI, there was a change in the element ratio of D-nZVI.

Surface Characterization of D-nZVI and nZVI XPS surface composition atom% Fe (Iron) B (Boron) S (Sulfur) nZVI 43.9 56.1 0.0 D-nZVI 57.2 36.8 6.0

Commonly, only a small amount of Fe ⁰ was found in the Fe (2p) spectra of nZVI and D-nZVI, which was determined to be due to oxidation during sample preparation (FIG. 4 (a)).

In addition, unlike nZVI in which both peaks of borate and boride were found in B (1s) spectrum of FIG. 4 (b), only peaks of borate were observed in D-nZVI and the sensitivity was also greatly reduced.

The sulfur component present in D-nZVI was found to be sulfide (S ^{2 −} ) depending on the binding energy value of the peak observed in S (2p) (FIG. 4 (c)). Considering the sensitivity of the peak and the elemental composition ratio, it was considered that the peak corresponding to Ferrous sulfide (707.0 eV) was not detected in the binding energy range of Fe (2p) because of the small amount. However, although the reaction equations (3) and (4) and SEM / EDX and XPS analysis results are small, ferrous sulfide precipitates are present on the surface of D-nZVI.

AFM / EFM analysis was performed using Dimension 3100 (Veeco, USA) to analyze the surface characteristics caused by precipitation of ferrous sulfide on the iron surface.

As a result of comparing surface roughness using AFM, as shown in FIG. 5, D-nZVI has a much rougher surface than nZVI. In R _rms value indicating the roughness of the surface D-nZVI it is greater than about twice nZVI having 24.5 nm to 44.9 nm.

EFM is a device that uses electrostatic force to measure electrical properties such as charge and conductivity on the sample surface. To do this, a voltage of +5 V is applied to the tip. The difference in conductivity of the surface is shown by the R _rms constant, which represents the contrast and vibration of the image. As shown in FIG. 6, the EFM image of D-nZVI is much brighter than nZVI, and the R _rms value is 1.60 °, which is about 6 times larger than 0.26 ° of nZVI. This indicates that the movement of electrons on the D-nZVI surface is more active. In fact, ferrous sulfide is known to be a highly conductive material due to the presence of delocalized electrons.

As compared with nZVI, D-nZVI synthesized through the addition of Dithionite increased both surface roughness and conductivity. Since the decomposition reaction of contaminants by nano-ferrous iron proceeds through the surface, the surface properties changed by ferrous sulfide are expected to have a great influence on the degradation of environmental pollutants.

Representative environmental pollutant purification test

4-1. Sodium dithionite  According to the added amount TCE  Reduction decomposition test

TCE digestion was carried out using 40 ml of amber vial running in a rolling mixer (15 rpm) by preparing 15 ppm of TCE solution using deionized water purged with N ₂ and then mixing with 0.08 g of D-nZVI. It was. Under the same experimental conditions, a vial containing no iron was used as a control.

Collect 0.1 ml of solution each hour in the reactor, mix 9.9 ml of deionized water and transfer to the headspace vial. TCE quantification was performed using a DB-624 (Alltech) column and a headspace-gas chromatography-electron capture detector (headspace GC / ECD, HP6890).

As described above, the reduction decomposition test for TCE was carried out, but the dithionite amount added in the synthesis was 0.1, 0.5, 1.0, 2.0, and 5.0 g / L, respectively, to compare the experimental results. As a result, as shown in FIG. 7, as the amount of Dithionite increases in the range of 0.1 to 2.0 g / L, the rate of TCE decomposition increases, but at 5.0 g / L, the rate decreases slightly. This is thought to be due to the inhibition of iron oxidation as the amount of ferrous sulfide deposited on the surface increases. Based on the above results, 2.0 g / L of dithionite was synthesized to obtain D-nZVI having the best TCE decomposition efficiency. It can be seen that it is preferable to use.

4-2. Nano Young Iron  By type TCE  Decomposition Rate Comparison

After dissolving 0.08 g of different types of nano-ferrous iron with 15 ppm of TCE solution, the decomposition rate was compared (FIG. 8).

In the case of RNIP, the BET surface area value published by the Toda group, which was sold without any measurement, was used, and the specific surface area was measured using the ASAP 2010 analyzer BET (Micromeritics, USA) for nZVI and D-nZVI only. The specific surface area of D-nZVI was 43.4 m ² / g, which is much larger than the specific surface area of 23-37 m ² / g of nano permanent iron reported in the literature. When comparing the specific surface area rate constant ( k _sa ), D-nZVI has a rate constant value that is twice as large as RNIP and up to 16 times larger than the synthesized nZVI (Table 2).

Comparison of reaction rate constants with various nano-ferrous irons Fe types BET surface area
(m ² / g) k _obs
(h ^-1 ) k _sa
(L? M ^-2 ? H ^-1 ) RNIP 23 0.411 ± 0.084 0.008 ± 0.002 nZVI 33.2 ± 0.2 0.080 ± 0.002 0.001 ± 0.00 D-nZVI 43.4 ± 0.1 1.59 ± 0.059 0.016 ± 0.001

This indicates that the newly synthesized D-nZVI has high reactivity with TCE. Based on the previous surface analysis results, this improved TCE reactivity is related to increased surface roughness and electrical conductivity.

The specific parts of the present invention have been described in detail above, and it is apparent to those skilled in the art that such specific descriptions are merely preferred embodiments, and thus the scope of the present invention is not limited thereto. something to do. Thus, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (10)

Dionion mediated nZVI (D-nZVI) with ferrous sulfide (FeS) precipitate attached to the surface
The method of claim 1,
The specific surface area of D-nZVI having the ferrous sulfide (FeS) precipitate attached to the surface is 40 to 60 m ² / g, which is larger than that of conventional nZVI.
The method of claim 1,
The surface roughness (Rrms) of D-nZVI having the ferrous sulfide (FeS) precipitate attached to the surface is 40-50 nm, which is larger than the surface roughness (Rrms) of conventional nZVI.
The method of claim 1,
The electrical conductivity of D-nZVI having the ferrous sulfide (FeS) precipitate attached to the surface thereof is about 6 times greater than that of conventional nZVI.
Method of preparing D-nZVI having a ferrous sulfide (FeS) precipitate attached to the surface of nanoferrous iron by adding sodium dithionite to sodium borohydride reducing agent used for nano-ferrous iron synthesis
The method of claim 5,
The manufacturing method comprises the steps of preparing a Fe ^{3 +} solution by dissolving ferric chloride (FeCl ₃ ) in water;
Sodium borohydride (NaBH ₄ ) was dissolved in water to prepare a sodium borohydride solution, and sodium dithionite (Na ₂ S ₂ O ₄ ) was added to the sodium borohydride solution to give NaBH ₄ -Na _2. S ₂ O ₄ Preparing an aqueous solution;
The NaBH ₄ -Na ₂ S ₂ O _{4 in} the Fe ^{3 +} solution Preparing D-nZVI coated with ferrous sulfide precipitate on the surface by dropwise adding an aqueous solution;
The ultrasonic wave is applied to the prepared D-nZVI, followed by washing with distilled water purged with nitrogen (N ₂ ) to remove impurities from the surface. D-nZVI manufacturing method comprising the
The method of claim 6,
D-nZVI manufacturing method characterized in that the concentration of the sodium dithionite (Sodium dithionite; Na ₂ S ₂ O ₄ ) is adjusted to 0.1 g / L ~ 5.0 g / L
The method of claim 7, wherein
D-nZVI manufacturing method characterized in that to adjust the addition concentration of the sodium dithionite (Na ₂ S ₂ O ₄ ) to 2.0 g / L to show the maximum decomposition efficiency of the pollutant
Method for purifying polluted soil and groundwater environmental pollutants, comprising reducing the environmental pollutants with D-nZVI on which ferrous sulfide (FeS) precipitate is attached to the surface.
10. The method of claim 9,
The environmental pollutants include trichloroethylene (TCE), tetrachloroethylene (PCE) chloride, polychlorinated biphenyl (PCBs), polychlorinated dibenzodioxins (PCDDs), polybrominated diphenyl ethers (PBDEs), trichloroethane (Trichoroethane; TCA); Tetrachloroethane (PCA), organic halogenated material of chlorinated methane; Heavy metals of chromium, lead, arsenic, nickel; Nitrate (NO3 ^-); Sulfate (SO 4 ^-2 ); Polycyclic aromatic hydrocarbons (PAH); chloroform; Nitrobenzene; Nitrotoluene; Dinitrobenzene; Method for purifying polluted soil and groundwater environmental pollutants, characterized in that selected from the group consisting of dinitrotoluene

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