WO2002040410A1

WO2002040410A1 - A remediation method of contaminated ground by injecting reactive material

Info

Publication number: WO2002040410A1
Application number: PCT/KR2000/001308
Authority: WO
Inventors: Jae-Won Lee; Jong-Jin Lee; Jun-Boum Park; Il-Chul Jung; Si-Hyun Kim; Sang-Su Lee
Original assignee: Halla Engineering & Industrial Developement Co., Ltd.; Geo Works Co., Ltd
Priority date: 2000-11-16
Filing date: 2000-11-16
Publication date: 2002-05-23
Also published as: JP2004528155A; JP3965118B2

Abstract

The present invention relates to a remediation method of the contaminated ground by injecting reactive materials, which is comprises of following steps: (i) transferring injection materials containing a reactive materials that directly react with the contaminated materials and an auxiliary injection materials to provide a mobility to the reactive materials so that the reactive materials can be easily transferred to the contaminated ground through the pores of the soil, to the contaminated ground which is located in the underground some distance from the surface by using the injection device of th remediation system; (ii) directly contacting the injection materials which is transferred to the contaminated ground as mentioned above (i) with the contaminated materials for a fixed time, and then extracting the contaminated water with the contaminated water extracting device of the remediation system followed by treating the extracted water with the extracted water treating device of the remediation system; (iii) reinjecting the extracted water which is treated with the extracted water treating device of the remediation system as mentioned above (ii) until the concentration of the contaminated materials in the contaminated water decreases to a certain level. According to this invention, the contaminated non-saturated zone in the soil where there is no underground water flow can be easily remedied.

Description

A REMEDIATION METHOD OF CONTAMINATED GROUND BY INJECTING

REACTIVE MATERIAL

Technical Field

The present invention relates to a method for remediation of contaminated ground by directly injecting reactive material, and more particularly to a method for remediation by injecting injection liquid that contains reactive material in suspension into contaminated ground and thereby causing reaction of these materials.

Background Art

In conventional ways of building a reactive wall for remediation of contaminated underground water, granular iron has been in use as reactive medium. 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 medium than when either of these materials was used separately. Meanwhile, USP 5,543,059 discloses a method for purification by passing contaminated material containing halogenated hydrocarbon through a tiered iron wall or column, comprising in at least three zones of graduated sizes of iron particles as reactive medium.

Above referenced conventional prior arts are characterized by removing the contaminated material by subjecting of the underground flow of water mixed with 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 to be 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 be in a cationic state. In the case of iron its redox potential is -0.44V.

Fe° <→ Fe² + 2e Formula (1) Fig.l is a diagram of the process of dechlorination of PCE (C₂C1₄, tetrachloroethylene) and its standard redox potential, Fig. 1, dechlorination gets the 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 exchanges 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 (Formula 4) and H₂O, etc.

FeA R + H^ Fe^ + 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 H₂ 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 needing high redox potential such as PCBs, because the iron particles has an limited redox potential when used without additionally treated or combined with other materials. Further, 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.

Still another problem was that such reactive walls were applicable to saturated zones of con-tamination where there were underground water flowing through, while, naturally enough, they were inapplicable to where there were no underground water flows.

Disclosure of Invention

With the view of solving such problems as mentioned above, the present invention provides a method for remediation of contaminated ground not merely in saturated but also in unsaturated zones, by injection of reactive materials into the contaminated strata.

Another objective of the present invention is to provide new reactive materials applicable to those contamination materials, requiring high redox potential such as PCBs.

The method of the present invention for remediation of contaminated ground by injection of re-active materials is characterized in that it consists of:

(i) a step of injecting the injection liquid, which contains both the reactive material to react with the contaminated materials in the ground and such injection- aiding material to give the said reactive material such mobility as to travel through pores of soil safely to a certain stratum of the ground where the contamination exists, away from the surface, by means of an injection device of the remediation system;

(ii) a step of extracting the contaminated water, by the use of an extracting device of the remediation system, an after having left the injection liquid in contact with the contaminated material for reaction for a certain length of time, and also of giving treatment to the extracted underground water by the use of an extracted water treatment device of the remediation system; and,

(iii) a step of re-injecting the treated extract water into the contaminated ground in repetition until it gets to a certain level of contamination by the use of the injection device of the remediation system.

In the present invention, the said "reactive materials" means such materials as remove the contamination materials in the ground or render them innocuous. They include irons including nanometer-scale irons, which have so far been in use as reactive material in this field or palladium-coated iron. These irons are applicable to ordinary organic chlorides such as chloroethylene or chloromethane which do not require very large energy in dechlorination, while the palladium-coated iron can be applied to such contamination materials such as PSBs which require large energy in dechlorination. Therefore, it is preferable that the less expensive nanometer-scale iron used in removal of ordinary organic chlorides and the more expensive palladium-coated iron is used for removal of PCBs and the like, requiring higher energy in dechlorination.

The said nanometer-scale iron used in removal of ordinary organic chlorides can be prepared by mixing 1.6M of sodium borohydride (NaBH₄) solution with 1.0M of ferric chloride (FeCl₃ ^• 6H₂O) solution in volume ratio of 1 : 3 and then slowly reacting with each other. In this reaction, the nanometer-scale iron is formed by the precipitation given in the following formula.

Fe(H₂O)₆ ^3" + 3BH₄ ^" + 3H₂O → Fe° J, + 3B(OH)₃ + 10.5H₂ (Formula 5)

The thus obtained nanometer-scale iron need not undergo any separate drying treatment but is injected, as it is, in the state of suspension into the contaminated stratum of ground.

The said palladium-coated iron is an iron which has been coated with palladium on the surface to increase the surface energy of nanometer-scale iron so that it can remove polycyclic hydrocarbons, such as PCBs. Palladium is a metal which has an atomic weight of 106.42amu, the melting point 1,554.9 ^°C, the boiling point 2,963 ^°C, and the specific gravity at 20 ^°C 1,202, and it has a unique power of absorbing hydrogen gas more than 900 times its own volume, thus proving a very useful catalyst for hydrogenation and dehydrogenation. In the present invention, too, palladium is used as catalyst for maximization of the effects in the reductive dechlorination of organic chlorides.

The said palladium-coated iron can be produced by pouring 5,000 wt parts of Fe into a solution of potassium hexachloropalladate (K₂PdCl₆) by 10 wt parts and water by 90 wt parts and having the surface of Fe coated with palladium until its orange color turns bright yellow. The following formula (6) shows this coating process.

PdCr + 2Fe^υ → Pd^υ + 2Fe _2²+⁺ + Cl^" (Formula 6)

The reactivity can be increased up to 500 — 1,000 times 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 1st order reaction of the conventional elemental iron.

the remediation of contaminated ground through the reactive zone formation in the present invention, it is preferable that said injection-aiding material can help the injection material be easily transferred to the contaminated strata, by securing mobilities into the small pores of the soil by lowering the viscosity of the reaction material. Therefore, the said injection-aiding material is required to have an excellent moisture containing ability among the negatively charged particles of soil particles and low surface tension. Materials with such properties include surfactants solutions.

The kinds of surfactants for use in the present invention and their characteristics follow:

(i) anionic surfactants

By these are meant those surfactants, the surface active parts of whose molecules are negatively charged. The anionic surfactants can have a relatively large mobility among soil particles because the anionic surfactants and soil particles repel each other because of their negative charges. The anionic surfactants usable in the present invention include:

carboxylates (RCOO^"M⁺), sulfonates (RSO₃ ^"M⁺), Sulfates (ROSO₃ ^"M⁺), and. Phosphates (ROPO₃ ^"M⁺), etc.

(ii) nonionic surfactant

By these are meant those surfactants, the surface active parts of whose molecules are not charged, and can be rendered either hydrophilic or hydrophobic and their surface tension is characteristically low. Thus the nonionic surfactants used as injection-aiding material in the present invention keep surface tension very low, thereby leading to a smooth flow of the injection liquid through pores of soil. Such nonionic surfactants include:

polyoxyethylenated slkylphenols (RC₆H₄(OC₂H₄)COH), polyoxyethylenes (-OCH₂CH₂O-), etc.

When the anionic and nonionic surfactants, as above mentioned, is used as an injection-aiding material, its concentration should be equal to or more than the minimum concentration where minimum point of the surface tension so called critical micell concentration (CMC) occurs. The critical micell concentration (CMC) for Neodol™ 25-3 is available from the Shell Company for an example as follows. Fig. 3 shows the changes of the surface tension of Neodol™ 25-3 ac cording to its different concentrations. As can be seen from Fig. 3, when its concentration reaches 0.032mM (0.0001% v/v) or over, its surface tension does not get any lower. Accordingly, in the case of Neodol™ 25-3 it is most preferable to use it at its minimum concentration, 0.032mM(0.0001% v/v). h Fig. 3, the said surface tensions were measured by the method of Du Nouy with the use of the Surface Tensiomat^R 21 (of Fisher Scientific Co., US).

An example of the remediation system in the present invention is illustrated in Fig. 7. As shown in FigJ., the system consists of a reactive material production device 88, a mixer 90, a pump 92, an injection device 94, an extraction device 96, and an extracted water treatment device 98. And the contaminated ground is divided in an unsaturated zone 100 and a saturated zone 102. The reactive material produced by the said reactive material production device 88 is transferred to the said mixer 90, where it is mixed with injection- aiding material, and after the mixture is stirred up lest the injection-aiding material should sink, the mixture is sent forward to the injection device 94 by a compression pump 92. Then the reactive material, mixed with its injection-aiding material transferred to the said injection device 94, is injected into the ground to react with the contaminated material in the soil. In the injection of the reactive material into the ground can be perforaied by a transferring means like a compressor also. The contaminated material which has reacted with the injected reactive material is extracted by the extraction device 96 and transferred to the extracted water treatment device 98. The extracted water thus treated at the extracted water treatment device 98 is transferred back to the injection device 94 for re- injection until its degree of contamination reaches a certain level.

For the above reactive material production device 88, an instance where nanometer scale elemental iron is used as reactive material, is illustrated in Fig. 8. To repeat, the nanometer-scale elemental iron is produced using a ferric chloride (FeCl₃ ^• 6H O) solution and sodium borohydride through the reaction given in Formula 1. The said reactive material production device consists of two reservoirs 118, 124, a reaction tank

128, a stirrer 130, nitrogen supply device 126, two pumps 108, 114, a washing water supply and its discharge device 104, a heating and magnetism induction device 110, and a mixer 112. From the two reservoirs 118, 124 respectively a ferric chloride (FeCl₃ ^• 6H O) solution 116 and a sodium borohydride (NaBH ) solution 122 are supplied to the reaction tank 128, where the nanometer scale iron is made through the reaction given in Formula 1 above. At this time the reaction needs to be performed evenly and thoroughly by the use of the stirrer 130. Also, by the use of the nitrogen supply device 126 nitrogen is to be constantly supplied for prevention of oxidation. After the reaction is complete the washing water is supplied by the washing water supply device 104, and after having the granules of iron held in the bottom for some time by means of the magnetic induction device 110, the impurities are washed off by extracting the suspended solution 106 of elemental iron mixed with impurities. The washed suspension solution 106 of elemental iron is transferred to the mixer 60 by the pump 114.

In the extracted water treatment device 98 of the remediation system the extracted water is filtered out to remove soil particles, and a required quantity of iron granules is added so that its contamination is lowered to get within the extent permitted by the environmental standards, before it is fed back to the injection device 94. The above treatment of extracted water is preferably performed someplace near the places of injection so that clogging under the ground can be prevented as much as possible, while evenly distributing iron granules. In this case the extracted water can directly be transferred to the injection device 94, necessitating no other separate transferring means for its transfer from the treatment device 98 to the injection device 94.

setting up the injection device 94 and the extraction device 96, the former 94 may be placed about 10m away from the latter, and through preparatory injection on the spot the depth and distance can be adjusted to suit the field conditions. An example of the setting up of both the injection device 94 and the extraction device 96 is given in Fig. 9. As shown in Fig.9., 9 of the injection device 94 is established in square way at 10m intervals and 4 of the extraction device 96 between them is established.

By leaving the reactive material which has reached the contaminated stratum of the ground to react with the contamination material there for some time, it is possible to decontaminate such a zone unsaturated with underground water, too, besides the saturated zones. For their reaction, the remediation system can be operated in various ways. For instance, after continuing injection and extraction in a direction for some time, it is possible to change course and continue in an alternate direction so that the reactive material is prevented from going one-sided by the flow of the fluid.

In the present invention it is possible, by effectively injecting the reactive material into the con-taminated strata of ground so as to have it directly react with the contaminated material, easily to decontaminate the ground even in an unsaturated zone, with no underground water flows.

Also, in the present invention, by the use of palladium-coated iron as reactive material it is pos-sible to obtain better effects even where unsaturated zones in the ground are contaminated than when nanometer-scale iron alone is used as reactive material.

Below, the present invention is described in more detail through examples. But as a matter of course these examples are given for illustration and the invention is never confined to these.

Brief Description of Drawings

Fig. 1 shows 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 talcing place by virtue of elemental iron over its surface;

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

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

Fig. 3 shows the changes of surface tension by different concentrations of Neodol™ 25-3;

Fig. 4 is an illustration of the columnar test device including the reactive material injection device in according to Example 1 ;

Fig. 5 shows the changes of concentration of PCE in according to Example 1;

Fig. 6 shows the changes of concentration of TCE in according to Example 1;

Fig. 7 shows an example of the remediation system which can be used in decontamination of contaminated ground by injection of the reactive material of the present invention;

Fig. 8 shows an example of the reactive material production device for the remediation system illustrated in Fig. 7; and, Fig. 9 is a plane view showing an example of establishment of the remediation system usable in the present invention.

Examples

For observation of the effects of the present invention a columnar test (Example 1) and a field application test (Example 2) were performed as follows:

Example 1

A columnar test was performed with a column contaminated with organic chlorides as follows. A column was filled with soil, and against samples of soil of natural water- content, and soil contaminated with water or other contaminating materials, respectively, the inj ection material was inj ected upward.

The testing device used here in is as shown in Fig. 4. As given in Fig. 4, the device consisted of a column 72, a pressure gauge 70 for measurement of the pressure in the pipe, a pump 74 for transfer of the contamination material and the reactive material, a reservoir 76 for storage of contaminated material, another reservoir 80 for storage of the reactive material and injection-aiding material, a nitrogen gas (N ) injection device 86 to inject the nitrogen gas for prevention of oxidation, a dissolved oxygen measurement gauge (DO meter) 84 to measure the concentration of oxygen inside the reactive material reservoir, and a stirrer 87 to prevent the reactive material in suspension from sinking down or coagulate.

After filling the column (diameter 4cm, length 100cm) with the soil, a solution saturated with lOOμM of PCE and another solution saturated with lOOμM of TCE were each injected into the above upwardly by 3~5 pore volume. The flow rate at this time was kept around 10^"3 cm/sec, resembling the actual underground current's. Next into the sample soil the injection material was injected upwardly, its flow rate kept at 10^"2cm/sec, nearly the same as that of the earlier injection. And after the injection of the injection material 0.01M of a CaCl₂ solution was pumped in at the same flow rate by 2 pore volumes.

Said injection material used herein includes nanometer-scale iron suspension; palladium-coated nanometer-scale iron suspension, in order to increase the dechlorination efficiency; nanometer-scale iron suspension together with nonionic surfactants (NEODOL^R 25-3), in order to secure the mobility into the pores of soil by lowering the surface tension between injection-aiding material and soil and further to maintain it as suspension state more longer time.

The water used in this test was deionized Milli-Q water (18.2MΩ^»cm, 5~10ppb TOC, Millipore, Corp), and it was degassed by 20min/L of nitrogen before use. When measured by a DO meter (Model 862A, Orion, USA) 84, the dissolved oxygen indicated 0.03mg/L. During the test, nitrogen was blown into the injection material reservoir 80. Inside the injection material reservoir 80 a stirrer 87 was installed to prevent Fe° from settling down. The production of lOOμM each of PCE and TCE was done, while stirring reaction vessel in the state of zero head space by the use of 0.6/ of Teflon gas sampling bag (Alltech, USA) for 12 hours in order to prevent the influence of upon volatilization. And the cooling each of PCE and TCE was filled in the column to produce the state of initial contamination conditions .

The concentration of PCE and TCE was each analyzed with gaschromatography (6890 Series, Hewlett Packard Co., USA), Table 1 shows the analytic conditions.

Table 1 : analytic conditions on gas chromatography

A certain amount of sample was taken from the contaminated water flowing out of the column as time passed, and the concentration each of PCE, TCE and Fe° each was measured, by which the merits of the present invention were appraised. After ascertaining that the concentration became settled the column was divided into 10 equal parts, and the concentration of iron inside each was measured. Also, the flow inside the column was veered for additional tests.

The distribution of iron inside the column was found relatively high near the injection point when the flow rate was slow and where the concentration of iron was relatively higher, but it was possible to make it even by changing the course of the flow inside the column. The amount of the flow at this time was set at about 1/3 that in the first direction.

Figs. 5 and 6 are drawings showing the results of this example, indicating particularly the change of concentration from the initials, of lOOμM PCE and lOOμM TCE aqueous solutions.

As shown in Figs. 5 and 6, the palladium-coated nanometer-level iron greatly improved the de-chlorination, and when NEODOL^S-S of 0.032mM concentration was added to it, removal of PCE and TCE was found improved, indicating that the injection- aiding material was relatively easily transferred to the organic materials which is trapped within the small pores of soil by its surface acting activity and thus the direct reaction was easily conducted.

Example 2

The remediation system of the present invention as shown in Figs. 7, 8, and 9, was established and it was tested with a stratum of ground contaminated with a aqueous solution of 3.55ppm TCE. The average water permeability coefficient of the ground was

10^"3~10^"4cm/sec, and the injection rate being kept at 3.0 x 10^"2 cm/sec. On a piece of land of 30m by 30m were established nine injection devices and four extraction devices at an average depth of 11m (See Fig. 9). A series of injections of injection material and its extractions was continued for 31 hours (De-contamination Step 1). Starting at three hours after the beginning of injection until the end of remediation process the extracted water was transferred to the injection devices and re-injected. The concentration of the contamination in the injection material was in the injection liquid 0.003% by weight.

After completion of this first step decontamination the direction of injection and extraction was changed to continue the operation of the system for 15 hours

(Decontamination Step 2). The results are as follows. Table 2: Concentrations each of TCE and iron in according to Example 2

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 ground by injecting reactive material, comprising the steps of:

(i) injecting an injection liquid containing a reactive material which is directly to react with contaminated material and injection-aiding material which is to aid the reactive material in its travel to reach contaminated strata of ground through small pores soil by giving it sufficient mobility and transferring the injection liquid to certain contaminated strata existing away from the surface of ground, by the use of an injection device of a remediation system;

(ii) extracting contaminated underground water by an extraction device of the remediation system after having the injection material which has reached the contaminated strata in contact with the contaminated material for a given length of time and thereafter giving treatment to the extracted underground water by means of a treatment device; and,

(iii) reinjecting by the injection device of the remediation system the extracted underground water after treatment at the extracted water treatment device of the system into the contaminated ground strata until it reaches a certain contamination level.

2. A remediation method of contaminated ground by injecting reactive material according to Claim 1, wherein said remediation system is comprised of a reactive material production device preparing the reactive material; a mixer for mixing the reactive material with injection-aiding material; a pump to transfer the injection liquid comprising of the reacting material and the injection-aiding material to an injection device; an injection device which by injection sends off the injection liquid to contaminated strata of land a certain depth away from the surface of ground by means of oil pressure; an extraction device to extract the contaminated underground water which has been reacted with the reactive material in the injection liquid for some time; and an extracted water treatment device which is to remove the precipitated impurities from the extracted underground water.

3. A remediation method of contaminated ground by injecting reactive material according to Claim 1, wherein the reactive material is either nanometer-scale iron or palladium- coated nanometer-scale iron.

4. A remediation method of contaminated ground by injecting reactive material according to Claim 1, wherein the injection-aiding material is either an anionic or nonionic surfactant.

5. A remediation method of contaminated ground by injecting reactive material according to Claim 3, wherein the anionic surfactant is selected from the group consisting of carboxylates, sulfonates, sulfates and phosphates.

6. A remediation method of contaminated ground by injecting reactive material according to Claim 3, wherein the nonionic surfactant is either polyoxyethylenated alkyl-phenol or polyoxyethylene.