WO2002040409A1

WO2002040409A1 - A REMEDIATION METHOD OF CONTAMINATED MATERIALS BY USING Pd/Fe BIMETALIC PERMEABLE GEOSYNTHETIC METAL LINER FOR THE REACTIVE WALL

Info

Publication number: WO2002040409A1
Application number: PCT/KR2000/001307
Authority: WO
Inventors: Jae-Won Lee; Jun-Boum Park; Tae-Sik Kim; Il-Chul Jung; Si-Hyun Kim; Sang-Su Lee
Original assignee: Halla Engineering & Industrial Development Co., Ltd.; Geo Works Co., Ltd.
Priority date: 2000-11-16
Filing date: 2000-11-16
Publication date: 2002-05-23
Also published as: JP4041735B2; JP2004529745A

Abstract

The present invention relates to a remediation method of contaminated materials by using Pd/Fe bimetalic permeable geosynthetic metal liner for the reactive wall, comprising the steps of preparing a permeable geosynthetic metal liner (PGML) for the reactive wall wherein non-woven geotextiles with crashed blast furnace slag attached thereon are adhered on both sides of reactive wall materials including mixture of iron which is coated with palladium which directly react with contaminant and soil, and installing the reactive wall at the area where contaminated materials pass, and eliminating contaminant by passing contaminated materials through said reactive wall. According to the present invention, the chlorinated organocompounds which need higher energy to dechlorinate can be effectively eliminated from the contaminated materials.

Description

A REMEDIATION METHOD OF CONTAMINATED MATERIALS BY USING Pd/Fe BIMETALIC PERMEABLE GEOSYNTHETIC METAL LINER

FOR THE REACTIVE WALL

Technical Field

The present invention relates to a remediation method of contaminated materials by using reactive wall and, more particularly, to a remediation method of contaminated materials by using reactive wall built under the ground where contaminated materials exist, whereby contaminated materials are eliminated by the chemical reaction of reactive media and contaminated materials induced by hydraulical flow of contaminant band of underground water. More specifically, the present invention uses flexible reactive wall to reduce the shock load of reacting materials due to the contaminated materials such as various organic materials and floating materials in the underground water, fn the flexible reactive wall, mixture of granular iron on which palladium is coated to directly react with contaminated materials, and soil fills two fold non- woven fabric like sandwich, and crushed non-woven geotextiles are attached. In addition, the present invention uses permeable geosynthetic metal liner (PGML) with two metals of palladium and iron which can be applicable to materials such as PCBs which require high redox potential, and can be produced in a large scale.

Background Art

In conventional ways of building a reactive wall for remediation of contaminated underground water, granular iron has been used as reactive media. For instance, USP 5,575,927 discloses a method for faster reduction of halogenated hydrocarbon by the use of mixture of iron and ferrous sulfide in relative quantities as reactive media than when either of these materials was used separately. And, USP 5,543,059 discloses a method for purification by passing contaminated material containing halogenated hydrocarbon through a tiered iron wall or column, comprising at least three zones of granule sizes of iron particles as reactive media.

Above referenced conventional prior arts are characterized by removing the contaminated materials by subjecting the underground flow of water containing contaminated material to pass through a reactive wall of granular iron, with no particular additives added thereto, built at strategic points for natural interception.

In above referenced prior arts the mechanism for removal of contaminated material by elemental iron is known as follows:

Iron existing as Fe° undergoes oxidation, forming redox couples. It resembles the corrosion caused by a spontaneous oxidation of elemental metals, which have a tendency to lose electrons and to be in a cationic state, hi the case of iron its redox potential is - 0.44V.

Fe° <→ Fe² + 2e^" Formula (1)

Fig. 1 is a diagram of the process of dechlorination of PCE (C C-U, tetrachloroethylene) and its standard redox potential. In Fig. 1, dechlorination gets slower, the farther it is from B to A. C indicates the point where the oxidation rate is the highest and D, the point where it is the lowest. As can be anticipated from Fig. 1, major reductants capable of reacting with organic chlorides are Fe°, Fe²⁺, and H₂. For instances of corrosion, the reaction is generally achieved by direct electron exchange between Fe° and alkyl chlorides adsorbed on the surface (Formula 2) but the reaction also may occur by Fe²⁺ produced from the corrosion (Formula 3), H₂ (Fonnula 4) and H₂O, etc.

Fe° + RX + H^,' <→ Fe²⁺ + RH + X: (Formula 2)

2Fe²⁺+ RX + H⁺ <→ 2Fe³⁺ + RH + X^" (Formula 3)

H₂ + RX ^ RH + H⁺ + X^" (Formula 4) '

Fig. 2 shows the reductive dechlorination of organic chlorides by exchange of electrons in corrosion of Fe°; Fig. 2A showing the reductive reaction of organic chlorides by Fe° which occurs on its surface; Fig. 2B, the reductive reaction of organic chlorides which occurs indirectly by way of ferrous ions; while Fig. 2C shows the role played by

Fe° in the reductive reaction of organic chlorides by H in the presence of catalyst.

The conventional reactive wall methods, as mentioned above, can only be applicable to the contaminated materials such as PCE, TCE, DCE, NC, CT and the like, but not to the contaminated materials such as PCBs which need high redox potential, because the granular iron has limited redox potential when used without additional treatment or addition of other materials. Furthermore, another problem was that against such contaminated materials which contain organic matters to a high degree, the surface energy of the iron particles used as reactive materials was found insufficient for satisfactory dechlorination. And, when the reactive wall is outworn, the conventional method has the problem of reconstructing the whole reactive wall system.

Disclosure of Invention

One object of the present invention is to solve problems as mentioned above and to provide reactive wall which can eliminate such material as PCBs that require high energy, and which includes reactive material that has reaction velocity of about 500 ~ 1000 times faster than conventional material which uses only granular iron so greatly reducing the thickness of reactive wall to 0.02 ~ 0.03 m while conventional reactive wall which uses granular iron of slow reaction velocity requires thickness of about 1 m to eliminate materials such as PCE, TCE, DCE, NC and CT.

Another object of the present invention is to provide flexible reactive wall to reduce the shock load of reacting materials due to the contaminated materials such as various organic materials and floating materials in the underground water. In this flexible reactive wall, mixture of granular iron on which palladium is coated to directly react with contaminated materials, and soil fills two fold non-woven fabric like sandwich, and crushed non- oven fabrics are attached. The remediation method of contaminated materials by using Pd/Fe bimetalic permeable geosynthetic metal liner for the reactive wall of the present invention comprises the steps of preparing a permeable geosynthetic metal liner (PGML) for the reactive wall wherein non-woven geotextiles with crashed blast furnace slag attached thereon are adhered on both sides of reactive wall materials including mixture of iron which is coated with palladium which directly react with contaminant and soil, and installing the reactive wall at the area where contaminated materials pass, and eliminating contaminant by passing contaminated materials through the reactive wall.

The palladium, which is used in the remediation method of contaminated materials by using Pd/Fe bimetalic permeable geosynthetic metal liner for the reactive wall of the present invention, is a metal which has atomic weight of 106.42 amu, melting point of

1,554.9 ^°C, boiling point of 2,963 °C, and the specific gravity at 20 ^°C of 1,202, and has been used as a very useful catalyst for hydrogenation and dehydrogenation since it has a unique power of absorbing hydrogen gas more than 900 times its own volume. In the present invention, the palladium is used as a catalyst to maximize the effect of the reductive dechlorination of organic chlorides. The palladium-coated bimetal iron can be produced by putting 5,000 wt parts of Fe into a solution which includes 10 wt parts of potassium hexachloropalladate (K PdCl₆) and 90 wt parts of water and by having the surface of Fe coated with palladium until its orange color turns bright yellow. The following formula (1) shows this coating process.

PdCl^6- + 2Fe° → Pd° + 2Fe²⁺ + Cl^" (Formula 1)

The reactivity can be increased up to 500 ~ 1,000 times higher by using above mentioned palladium-coated iron, than that of the conventional method using elemental iron because the palladium/iron bimetal of the present invention undergoes zero order reaction rather than 1 st order reaction of the conventional elemental iron.

Figs. 3 and 4 illustrate one example of the permeable geosynthetic metal liner used in the remediation method of contaminated materials by using Pd/Fe bimetalic permeable geosynthetic metal liner for the reactive wall of the present invention.

Fig. 3 illustrates one example of the permeable geosynthetic metal liner of steel wool type. As shown in the figure, in order to filter off floating materials, non-woven geotextiles 20 are adhered on both sides of reactive wall materials including Pd/Fe bimetal which directly react with the contaminant. The non-woven geotextile 20 of the present invention is adhered to reduce the shock load of reacting materials due to the contaminated materials. Crashed blast furnace slag, which is a byproduct of steelmaking process in the steel industry and is very cheap and has excellent absorption characteristics, can be attached on the non- woven geotextile 20. Steelwool 10 coated with palladium is used as Pd/Fe bimetal.

But, when iron of steelwool type is used as a reactive wall, contaminated materials can pass without reacting with the reactive media due to the space between steelwools 10. Therefore it is desirable to use granular iron coated with palladium, which has similar reactivity as the steelwool coated with palladium.

Fig. 4 illustrates one example of the permeable geosynthetic metal liner of granular iron type. As shown in the figure, granular iron 30 coated with palladium is used as Pd/Fe bimetal. When contaminated ground is composed mainly of silt or clay it is desirable to use iron of steelwool type since the strength of reactive media can be maintained against twist of the ground, and when contaminated ground is composed mainly of sandy soil it is desirable to use granular iron type. Both type of iron is coated with palladium as a catalyst.

The reason non- woven geotextiles with crashed blast furnace slag attached thereon is attached on both sides of the reactive media is as follows. The effectiveness of reaction of reactive media can be lowered due to the competition with the floating materials, nutrient salts and heavy metals in underground water, and the interaction with chemical precipitation. The introduction of these floating materials, nutrient salts and heavy metals must be prevented in advance. Therefore the present invention attaches, on both sides of reactive wall materials, non-woven geotextiles with crashed blast furnace slag, which is a byproduct of steehnaking process in the steel industry and is very cheap and has excellent absorption characteristics of the floating materials, nutrient salts and heavy metals, attached thereon in order to prevent the lowering of effectiveness of reaction of reactive media composed of Pd/Fe bimetal due to the introduction of impurities into the system. The absorption characteristics of the nutrient salts by blast furnace slag can be shown from Figs. 5 and 6. Figs. 5 and 6 are the result of measuring the change of concentration of ammonia and phosphate in 1 litter of water solution of ammonia with concentration 20mg/l and 1 litter of water solution of phosphate with concentration 500mg/l caused by the absorption of ammonia and phosphate by blast furnace slag. The size of blast furnace slag is 1 m in breadth, 0.5 m in length and 0.005 m in thickness. As can be seen in Fig. 5, the concentration of ammonia in the solution is changed to 16.35 mg/1 after 72 hours and 18.2% of ammonia is eliminated by absorption. As can be seen in Fig. 6, the concentration of phosphate in the solution is changed to 316 mg/1 after 72 hours and 36.8% of phosphate is eliminated by absorption. As can be seen in these result, blast furnace slag has excellent absorption characteristics on the floating materials, nutrient salts and heavy metals, and is appropriate for eliminating these materials by absorption.

The content of nanometer scale iron coated with palladium of the present invention is preferably 5 ~ 20 wt% and most favorably 20 wt% of the whole reactive materials. If the content is larger than 20 wt%, the permeability of the reactive wall is lowered, reducing the effectiveness of remediation of contaminated materials. And if the content is smaller than 5 wt%, the amount of palladium coated iron becomes too small, also reducing the effectiveness of remediation of contaminated materials.

The permeable geosynthetic metal liner (PGML) for the reactive wall with Pd Fe bimetal can be made in any form and can be made in a certain standard to be made in a large scale installed at the site easily.

The method of the present invention can be applicable to contaminated materials of organic compounds such as PCE(C₂Cl4_. tetrachloroethylene), TCE(C₂HC1₃, trichloroethylene), DCE(C₂H₂C1₂, dichloroethylene), NC(C₂H₃C1, vinyl chloride),

CT(CC1₄, carbon tetrachlori.de), trichloromethane(CHCl₃), dichloromethane(CH₂Cl₂), chloromethane(CH Cl) and PCBs(polychlorinated biphenyls). These organic compounds are converted into harmless materials such as ethane through reductive dehalogenation reaction which replaces Cl^" ion with H ^" ion by the electron generated by corrosion process of Fe°.

Since the palladium coated iron used in the present invention as reactive material is much more reactive than the conventional reactive wall system using only soil and Fe°, the thickness of the reactive wall can be reduced. Also, by using the method of the present invention, organic chloride such as PCBs which requires high dechlorination energy can be effectively eliminated.

In addition, since the permeable geosynthetic metal liner (PGML) for the reactive wall with Pd/Fe bimetal can be made in a predetermined form, it can be standardized and can be made in a large scale and easily installed at the site.

Brief Description of Drawings

Fig. 1 illustrates the process of dechlorination of PCE and the standard redox potential;

Fig. 2A is a drawing to show the reductive reaction of an organic chloride directly taking place by virtue of elemental iron over its surface;

Fig. 2B illustrates the role of elemental iron in a reductive reaction of an organic chloride indirectly taking place by virtue of ferrous ion;

Fig. 2C illustrates the role of elemental iron in a reductive reaction of an organic chloride by H₂ in the presence of catalyst;

Fig. 3 illustrates one example of the permeable geosynthetic metal liner of steel wool type;

Fig. 4 illustrates one example of the permeable geosynthetic metal liner of granular iron type;

Fig. 5 shows the change of concentration of TCE after passing the 100 μM solution of TCE through the reactive wall of Pd/Fe bimetalic permeable geosynthetic metal liner;

Fig. 6A is a chromatogram of the components of congener of 20 ppm PCB(arochlor- 1254);

Figs. 6B and 6C are chromatograms of the components of PCBs after passing 20 ppm solution of PCBs through the reactive wall of Pd/Fe bimetalic permeable geosynthetic metal liner of example 2 for 10 and 24 hours respectively;

Fig. 7 shows the change of concentration of PCE after passing 100 μM solution of

PCE through the reactive wall of Pd/Fe bimetalic permeable geosynthetic metal liner which includes palladium coated granular iron and normal granular iron;

Fig. 8 shows the change of concentration of TCE after passing 100 μM. solution of TCE through the reactive wall of Pd/Fe bimetalic permeable geosynthetic metal liner which includes palladium coated granular iron and normal granular iron;

Fig. 9 shows the change of concentration of ammonia when the solution of ammonia with initial solution of 20mg/l is in equilibrium with blast furnace slag; and

Fig. 10 shows the change of concentration of phosphate when the solution of phosphate with initial solution of 500mg/l is in equilibrium with blast furnace slag.

Examples

Now the present invention will be described in detail with reference to the examples. These examples are for the purpose of illustration only, and not intended to limit the present invention.

Example 1

hi this example, the reactive wall of Pd Fe bimetalic permeable geosynthetic metal liner is installed with breadth lm, length 0.5m and thickness 0.005m, and solutions of lOOi/M of TCE and 20 ppm of PCBs(Arochlor-1254) are passed through the reactive wall.

The effect of the remediation method of contaminated materials by using Pd/Fe bimetalic permeable geosynthetic metal liner for the reactive wall of the present invention is evaluated by measuring the concentration of TCE and PCBs of the passed solution as time goes by. The content of palladium coated iron in the metal liner of this example is 20wt%.

The hydraulic conductivity of the reactive wall of Pd/Fe bimetalic permeable geosynthetic metal liner is measured as 5cm/hr, and the hydraulic gradient 1/50. Darcy flow velocity calculated from above data is O.lcm/hr and maximum velocity of the underground water is set as lcm hr which is 10 times the above flow velocity.

In order to reduce the effect of volatilization, the solution of 100 /M TCE used in this example is prepared by stirring for 12 hours in zero headspace state by using 0.61 of Teflon gas sampling bag (Alltech, USA). Also, the solution of 20mg/l PCBs is mixed with 1 ml of Arochlor-1254 (lOOi/g/ml methanol, ACS reagent, 99.8%+, Sigma, USA) and 3ml of 20% methanol solution, and 1 ml of acetone (ACS reagent, 99.8%+, Sigma, USA) is added to the solution for complete dissolution of Arochlor-1254. The ratio of concentration of methanol/water/acetone is 1 : 3: l(v/v/v).

The concentration of TCE used in this example is analyzed by using gas chromatography (6890 series, Hewlett Packard Co, USA). The condition for gas chromatography is shown in Table 1.

Table 1. condition for gas chromatography

The concentration of Arochlor-1254 used in this example is analyzed by using gas chromatography (6890 series, Hewlett Packard Co, USA) according to the extraction method of hexane (reagent grade, showa chem., Japan). The condition for gas chromatography is shown in Table 2. Table 2. condition for gas chromatography

The results of this example are shown in Figs. 7 and 8. Fig. 7 shows the change of concentration of TCE after passing 100 μM solution of TCE through the reactive wall of Pd/Fe bimetalic permeable geosynthetic metal liner which includes palladium coated iron. As shown in the figure, the reactive wall of steelwool type is lower in effectiveness than the reactive wall of granular iron type. From this result it can be directly confirmed that the mechanism of remediation is closely related with the size of reactive materials.

Fig. 8 shows the change of concentration of PCBs after passing 20ppm solution of PCBs through the reactive wall of Pd/Fe bimetalic permeable geosynthetic metal liner which includes palladium coated iron. As shown in the figure, it can be known from the relative peak area of PCBs, namely the concentration of PCBs remaining in the solution, that most PCBs in the solution are eliminated after 24 hours. Fig. 8 A in Fig. 8 illustrates the peak area of each single element of 20ppm PCBs (arochlor-1254) congener. Fig. 8B and Fig. 8C illustrate the peak area of each single element of PCBs after passing solution of 20ppm PCBs (arochlor-1254) congener through the reactive wall of Pd/Fe bimetalic permeable geosynthetic metal liner for 10 and 24 hours.

Example 2

The purpose of example 2 is to compare the reaction velocity of Pd/Fe bimetalic permeable geosynthetic metal liner which uses palladium coated iron as a reactive material, and conventional permeable geosynthetic metal liner which uses elemental iron Fe° as a reactive material.

For this comparison, Pd/Fe bimetalic permeable geosynthetic metal liner which uses palladium coated iron as a reactive material, and conventional permeable geosynthetic metal liner which uses elemental iron Fe as a reactive material are prepared, and PCE and TCE of 100 βM are passed through each of two metal liners, and the concentration is measured after predetermined time.

The conditions of this example is the same as those of example 1 except that conventional permeable geosynthetic metal liner which uses elemental iron Fe° is also used.

The results of this example are shown in Figs. 9 and 10. Fig. 9 shows the change of concentration of PCE in this example and Fig. 10 shows the change of concentration of TCE in this example. According to the result shown in Fig. 9, initial lOOi M of PCE is reduced to 28.8 /M after 50 hours in the case of onventional permeable geosynthetic metal liner showing elimination of 71.2%, while the concentration is reduced to 5.44 /M after 0.017 hours in the case of Pd/Fe bimetalic permeable geosynthetic metal liner showing elimination of 94.5%. According to the result shown in Fig. 10, initial 100_./ of TCE is reduced to

38.1/M after 50 hours in the case of onventional permeable geosynthetic metal liner showing elimination of 61.9%, while the concentration is reduced to 4.6]JM after 0.017 hours in the case of Pd/Fe bimetalic permeable geosynthetic metal liner showing elimination of 95.4%.

Industrial Applicability

The present invention relates to environmental industries, and especially to land environmental industries, thus being applicable to industrial estates and military facilities such as underground oil storage facilities, semi-conductor plants, areas of heaving populated with plants, petrochemical engineering facilities, etc. for instance.

Claims

ClaimsWhat is claimed is:

1. A remediation method of contaminated materials by using Pd/Fe bimetalic permeable geosynthetic metal liner for the reactive wall, comprising the steps of preparing a permeable geosynthetic metal liner (PGML) for the reactive wall wherein non-woven geotextiles with crashed blast furnace slag attached thereon are adhered on both sides of reactive wall materials including mixture of iron which is coated with palladium which directly react with contaminant, and soil, and installing the reactive wall at the area where contaminated materials pass, and eliminating contaminant by passing contaminated materials through said reactive wall.

2. The remediation method of contaminated materials by using Pd/Fe bimetalic permeable geosynthetic metal liner for the reactive wall according to claim 1, wherein said palladium coated iron is prepared putting 5,000 wt parts of Fe into a solution which includes 10 wt parts of potassium hexachloropalladate (K₂PdCl₆) and 90 wt parts of water and by having the surface of Fe coated with palladium until its orange color turns bright yellow.

3. The remediation method of contaminated materials by using Pd/Fe bimetalic permeable geosynthetic metal liner for the reactive wall according to claim 1, wherein said palladium coated iron is granular irons coated with palladium, or mixture of granular irons coated with palladium and steel wool coated with palladium.

4. A permeable geosynthetic metal liner (PGML) for the reactive wall wherein non- woven geotextiles with blast furnace slag attached thereon are adhered on both sides of palladium coated iron.