Method for purifying contaminated soil and contaminated water

Abstract

To provide a method for purifying soil and groundwater which is capable of efficiently and reliably purifying the soil and groundwater contaminated with chemical substances.SOLUTION: A method for purifying soil and groundwater according to the present invention is intended to purify soil and groundwater 102 contaminated with chemical substances, characterized by injecting persulfate, iron salt, and saccharides into the soil and groundwater.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for purifying soil and water contaminated by chemical substances. [Background technology]

[0002] In factories and other facilities, organic chlorine compounds such as trichloroethylene (TCE) and tetrachloroethylene (PCE), and aromatic hydrocarbons such as benzene (hereinafter referred to as "chemical substances") are widely used. Some of these chemical substances are carcinogenic and other harmful, and in recent years, soil and groundwater contamination by these chemical substances has become a major issue.

[0003] As one method for purifying soil and groundwater contaminated with chemical substances, for example, Patent Document 1 discloses a "method for treating chemical contamination in which persulfate and organic acid iron are injected into soil and groundwater contaminated with chemical substances to purify the soil and groundwater at an acidic pH level." According to Patent Document 1, this configuration makes it possible to treat chemical substances in soil and groundwater contaminated with chemical substances more safely and efficiently than conventional treatments using persulfate.

[0004] Patent Document 2 discloses that "a chemical substance decomposition composition (excluding iron ions) comprising (A) at least one type of peroxide (e.g., persulfate) and (B) at least one selected from the group consisting of unsaturated carboxylic acids, hydroxycarboxylic acids, monosaccharides, and disaccharides" is brought into contact with soil, groundwater, etc. contaminated with chemical substances to decompose the chemical substances. Patent Document 2 also discloses that difficult-to-decompose substances such as carbon tetrachloride can be oxidatively decomposed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5368201 [Patent Document 2] JP 2017-043706 A Summary of the Invention [Problem to be solved by the invention]

[0006] According to Patent Document 1, it is possible to treat chemical substances contained in soil or groundwater by injecting persulfate and organic iron salt. According to Patent Document 2, (A) at least one type of peroxide is mixed with (B) at least one selected from the group consisting of unsaturated carboxylic acids, hydroxycarboxylic acids, monosaccharides, and disaccharides (iron ions are excluded). However, neither method can be said to have a high decomposition effect, and there was a need to further improve efficiency.

[0007] In view of the above problems, the present invention aims to provide a method for remediating soil and groundwater that can reliably purify soil and groundwater contaminated by chemical substances with high efficiency. [Means for solving the problem]

[0008] In order to solve the above problems, a representative configuration of the soil and groundwater purification method of the present invention is a soil and groundwater purification method for purifying soil and groundwater contaminated by chemical substances, which is characterized by injecting persulfate, iron salt, and sugars into the soil or groundwater or mixing them with the soil. Effect of the Invention

[0009] According to the present invention, there is provided a soil / groundwater remediation method capable of highly efficiently and reliably purifying soil and groundwater contaminated by chemical substances. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating a method for purifying soil and groundwater according to an embodiment of the present invention. [Diagram 2] 1 is a graph illustrating the promoting effect of sugar on the decomposition of TCE. [Diagram 3] 1 is a graph illustrating the effect of monosaccharides in promoting the decomposition of TCE. [Figure 4] 1 is a graph illustrating the effect of disaccharides in promoting the decomposition of TCE. [Diagram 5] 1 is a graph illustrating the effect of polysaccharides in promoting the decomposition of TCE. [Figure 6] FIG. 1 is a diagram illustrating a comparison of the TCE decomposition promoting effect according to the classification of saccharides. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. The dimensions, materials, and other specific values ​​shown in the embodiment are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are given the same reference numerals to avoid repeated explanations, and elements not directly related to the present invention are not shown.

[0012] Fig. 1 is a diagram for explaining a method for purifying soil and groundwater according to this embodiment. In the soil remediation method of this embodiment, persulfate, iron salt, and sugars are injected into the soil and groundwater 102 through an injection pipe 104 arranged in the soil as shown in Fig. 1, thereby purifying the soil and groundwater 102 contaminated with organochlorine compounds such as trichloroethylene (TCE) and tetrachloroethylene (PCE) and aromatic hydrocarbons such as benzene (hereinafter, these are referred to as chemical substances 110).

[0013] The persulfate is not particularly limited, and known and commonly used persulfates can be used. Examples of persulfates include potassium peroxomonosulfate (also called potassium hydrogen persulfate, potassium monopersulfate, or potassium hydrogen monopersulfate), sodium peroxymonosulfate, ammonium peroxymonosulfate, potassium peroxodisulfate, sodium peroxodisulfate, and ammonium peroxodisulfate. These persulfates may be used alone or in combination of two or more. Examples of iron salts include iron(II) chloride, iron(III) chloride, iron(II) nitrate, iron(III) nitrate, iron(II) sulfate, and iron(III) sulfate. Examples of sugars that can be used include monosaccharides, disaccharides, and polysaccharides.

[0014] In theory, persulfate, iron salt, and sugar can be added at the same time. However, when adding to the soil and groundwater on-site, it is more effective to add the iron and sugar after the persulfate. This allows the chemicals to reach farther in the underground environment. If there is a well, they can also be added from the well to the groundwater vein, or the chemicals can be mixed directly into the soil.

[0015] The effects of the soil and groundwater purification method of this embodiment will be described below with reference to the drawings. In the graphs of the drawings referred to below, the vertical axis represents TCE concentration (mg / L) and the horizontal axis represents time (h).

[0016] FIG. 2 is a graph illustrating the promoting effect of sugar on the decomposition of TCE. In Example 1, the substance amount ratio of persulfate, iron sulfate as an iron salt, glucose as a sugar, and TCE is 20:5:2:1. In Comparative Example 1, the substance amount ratio of persulfate, iron sulfate as an iron salt, glucose as a sugar, and TCE was 20:5:0:1. That is, in Comparative Example 1, no sugar was added. In Comparative Example 2, the substance ratio of persulfate, iron sulfate as an iron salt, glucose as a sugar, and TCE was 20:0:2:1. In other words, in Comparative Example 2, no iron salt was added. In Comparative Example 3, the substance amount ratio of persulfate, iron sulfate as an iron salt, glucose as a sugar, and TCE was 0:5:2:1. That is, in Comparative Example 3, no persulfate was added. In Comparative Example 4, the substance amount ratio of persulfate, iron sulfate as an iron salt, glucose as a sugar, and TCE was 0:0:2:1. That is, in Comparative Example 4, no persulfate or iron salt was added.

[0017] As shown in Fig. 2, in Example 1, in which persulfate, ferrous sulfate as an iron salt, and glucose as a sugar were all added, the TCE concentration decreased significantly over time, reaching nearly 0% after 5 hours. In contrast, in Comparative Examples 1 to 4, in which one or two of persulfate, ferrous sulfate as an iron salt, and glucose as a sugar were added, the TCE concentration fluctuated slightly over time, but no significant decrease was observed. This shows that a high TCE decomposition effect can be obtained by adding sugars together with persulfate and ferrous sulfate, as in the soil / groundwater purification method of this embodiment.

[0018] FIG. 3 is a graph illustrating the promoting effect of monosaccharides on the decomposition of TCE. In Example 1, glucose is used as the monosaccharide. In Example 2, fructose is used as the monosaccharide. In Example 3, galactose is used as the monosaccharide. In Example 1-3, the substance amount ratio of the persulfate, iron sulfate as an iron salt, monosaccharides and TCE was 20:5:2:1.

[0019] As shown in Example 1-3 in Fig. 3, when monosaccharides are used as sugars, the TCE concentration decreases over time and eventually reaches nearly 0%, regardless of the type of monosaccharide. In contrast, in Comparative Example 1, the TCE concentration after 7 hours remains at about 60%. This shows that the soil / groundwater purification method of this embodiment can achieve a high TCE decomposition effect regardless of the type of monosaccharide.

[0020] FIG. 4 is a graph illustrating the promoting effect of disaccharides on the decomposition of TCE. In Example 4, maltose is used as the disaccharide. In Example 5, sucrose is used as the disaccharide. In Example 6, lactose is used as the disaccharide. In Examples 4-6, the substance amount ratio of the persulfate, iron sulfate as an iron salt, the disaccharide, and TCE was 20:5:2:1.

[0021] As shown in Example 4-6 in Fig. 4, even when disaccharides are used as the saccharides, the TCE concentration decreases with time, regardless of the type of disaccharide. In Comparative Example 1, the TCE concentration after 7 hours remains at about 60%. This shows that the soil / groundwater purification method of this embodiment can achieve a high TCE decomposition effect regardless of the type of disaccharide.

[0022] 4, it takes 7 hours for the TCE concentration to reach 0% in Examples 4 and 6, whereas it takes 5 hours for the TCE concentration to reach 0% in Example 5. Therefore, it can be seen that, as disaccharides, sucrose has the highest TCE decomposition effect among maltose, sucrose, and lactose.

[0023] FIG. 5 is a graph illustrating the effect of pectin, a polysaccharide, in promoting the decomposition of TCE. In Example 7, guar gum is used as the polysaccharide. In Example 8, chitosan is used as the polysaccharide. In Example 9, pectin is used as the polysaccharide. In Example 10, xanthan gum is used as the polysaccharide. In Examples 7-10 and Comparative Example 5, the substance ratio of persulfate, iron sulfate as an iron salt, and TCE was 20:20:1. 5.2 g / L of polysaccharide was added.

[0024] As shown in FIG. 5, in Comparative Example 1, the TCE concentration decreased to about 70% after 30 minutes, and thereafter stagnated in the range of 65% to 60%. In contrast, in Examples 7 to 10, the decomposition progressed with time. Even in Example 7 (guar gum), which had the least effect, the TCE concentration was below 40% after 3 hours. In Example 10 (xanthan gum), which had the highest effect, the TCE concentration was almost zero after 30 minutes. From these results, it can be seen that by adding a polysaccharide together with a persulfate and an iron salt, a higher TCE decomposition effect can be obtained compared to when they are not added.

[0025] FIG. 6 is a diagram illustrating a comparison of the TCE decomposition promoting effect according to the classification of saccharides. In Example 11, 5.2 g / L of glucose, a monosaccharide, was added. In Example 12, 5.2 g / L of sucrose, a disaccharide, was added. In Example 9, 5.2 g / L of pectin, a polysaccharide, was added. In Examples 7-9, the weight ratio of the persulfate, iron sulfate as the iron salt, and TCE was 20:20:1. In addition, in Fig. 6, the horizontal axis of the graph represents time (h). Example 11 has the same material composition as Example 1, but the amounts are different, so the example number is different. Similarly, Example 12 has the same material composition as Example 5, but the amounts are different, so the example number is different.

[0026] As shown in Fig. 6, the TCE concentration decreases over time when any of Examples 9, 11, and 12 was added. At this time, among Examples 9, 11, and 12, the TCE concentration at the time point when 210 minutes had elapsed was lowest in the order of Example 11, Example 12, and Example 9. From this, it can be understood that, among monosaccharides, disaccharides, and polysaccharides, polysaccharides (pectin) has the greatest TCE decomposition effect.

[0027] As described above, according to the soil / groundwater purification method of this embodiment, TCE can be decomposed with high efficiency by using persulfate, iron salt, and sugars in combination, and high soil / groundwater purification performance can be obtained. In addition, since sugar is less expensive as a reagent unit price than organic acid, the cost of soil / groundwater purification treatment can be significantly reduced. Furthermore, since food processing residue sugar waste can be used as sugar, it is possible to further reduce the cost of purification treatment and contribute to promoting the reuse of waste.

[0028] Although the preferred embodiment of the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such an embodiment. It is clear that a person skilled in the art can think of various modifications or alterations within the scope of the claims, and it is understood that these also naturally belong to the technical scope of the present invention. [Industrial Applicability]

[0029] The present invention can be used as a method for purifying soil and groundwater contaminated by chemical substances. [Explanation of symbols]

[0030] 102...soil and groundwater, 104...injection pipes, 110...chemicals

Claims

[Claim 1] A method for purifying soil and groundwater contaminated by chemical substances, comprising: A method for purifying soil and groundwater, comprising injecting persulfate, iron salt and sugar into the soil and groundwater.

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