KR20040014334A - Soil treatment agent and soil treating method - Google Patents

Abstract

PURPOSE: Provided are a soil treating agent which comprises a first material capable of discharging iron ions, and a second material capable of discharging hydrogen, and can effectively remove dioxins from soil, and a soil treatment method using the same. CONSTITUTION: The soil treating agent comprises the first material and the second material, wherein the first material is Fe2O3, and the second material is at least one of sodium hydrogen sulfite and sodium thiosulfate. The soil treating agent comprises 10-300 parts by weight of the second material with respect to 100 parts by weight of the first material. The soil treatment method comprises adding the soil treating agent to the soil. A moisture content of mixture of the solid and the soil treatment agent is 30-300 wt% based on solid of the mixture.

Description

Soil treatment agent and soil treating method

The present invention relates to a soil treatment agent and a soil treatment method, in particular a soil treatment agent and a treatment method containing dioxins.

Soil pollution due to dioxins in fly ash or dioxins in pesticides emitted from incineration facilities such as industrial waste and household waste has become a serious problem. Here, dioxins include polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (Co-PCBs). It is a generic term such as skin trouble and visceral disorder, and it is an unprecedented toxic substance having teratogenicity or malformation or carcinogenicity. In particular, the narrow dioxin 2,3,7,8-dibenzoparadioxin is one of the most toxic substances available to humans.

Soil contamination from these dioxins is likely to cause secondary pollution to the surrounding environment or flora and fauna. In particular, when agricultural land such as rice fields or fields are contaminated by dioxin, the human body may be seriously contaminated through crops.

An object of the present invention is to effectively remove dioxins contained in the soil.

The soil treatment agent of the present invention includes a first material capable of releasing iron ions and a second material capable of releasing hydrogen. The first material used here is, for example, ferric trioxide (Fe ₂ O ₃ ). On the other hand, the second substance used here is at least one of sodium hydrogen sulfite and sodium thiosulfate. This soil treatment agent usually contains 10 to 300 parts by weight of the second substance with respect to 100 parts by weight of the first substance.

In addition, the soil treatment method of the present invention includes a step of mixing by adding a soil treatment agent containing a first substance capable of releasing iron ions and a second substance capable of releasing hydrogen to the soil. In this method, 1 to 50 parts by weight of the soil treatment agent is usually added to 100 parts by weight of soil and mixed. In this method, it is preferable to set the amount of water in the mixture of the soil and the soil treatment agent to be usually 30 to 300% by weight of the total solids of the mixture.

In addition, the soil treatment method according to another aspect of the present invention includes a step of adding and mixing the first substance capable of releasing iron ions and the second substance capable of releasing hydrogen, respectively, in the soil. In this method, 1 to 50 parts by weight of the first substance and the second substance are usually added to 100 parts by weight of soil and mixed. In this method, it is usually preferable to set the ratio of the second substance to 100 parts by weight of the first substance to 10 to 300 parts by weight. Moreover, in this method, it is preferable to set the amount of water in the mixture containing the soil, the first substance and the second substance to be 30 to 300% by weight of the total solids of the mixture.

The first substance contained in the soil treatment agent of the present invention is one capable of releasing iron ions, particularly one capable of releasing iron ions into water. Such a first material is not particularly limited but is preferably capable of releasing trivalent iron ions. Specific examples of such a first substance include ferric trioxide (Fe ₂ O ₃ ) and iron oxide (FeO). Of these, it is preferable to use ferric trioxide.

Here, the above-mentioned ferric trioxide is usually called magnetite, and the manufacturing method is not particularly limited, but is preferably obtained by, for example, a sulfuric acid method titanium oxide production process. Specifically, the iron-containing sulfuric acid obtained in the sulfuric acid method titanium oxide production process is neutralized and then concentrated / separated. The filtrate obtained by filtering the supernatant liquid at this time is neutralized and oxidized again. Specifically, sodium hydroxide is added while passing the air stream through the filtrate, and the temperature is set at 65 ° C, so that the pH is 6.0 to 6.3 and the oxidation rate is 75 to 80%. And the product obtained by such neutralization and oxidation treatment is isolate | separated by filtration, and then drying at about 120 degreeC, the target ferric trioxide is obtained. In addition, it is preferable to perform a final drying process in nitrogen atmosphere. In this way, ferric trioxide having a higher decomposition efficiency of dioxins is obtained.

The first substance as described above is preferably in the form of a powder. More specifically, a powder form having an average particle diameter of 0.2 to 50 µm is preferable, and a powder form having an average particle diameter of 0.3 to 10 µm is more preferable. However, the particle shape is not particularly limited. In addition, when the first component is the above-mentioned ferric trioxide, the method and conditions for making it into powder form are not particularly limited, but in general, in order to avoid the reaction of the ferric trioxide with water and oxygen, an anhydrous nitrogen stream Preference is given to pulverizing and drying underneath.

In addition, the second material used in the soil treatment agent of the present invention is one capable of releasing hydrogen, in particular one capable of releasing hydrogen into water. Although such a second material is not particularly limited, it is preferable that hydrogen can be released in an ionic state. In this specific example of such a second material examples include, for example, there may be mentioned sodium bisulfite (NaHSO _3), sodium thiosulfate _{(Na 2 S 2 O 3)} , sodium borohydride (NaBH _4). Among these, at least one of sodium hydrogen sulfite and sodium thiosulfate is preferably used.

The second material as described above is preferably in the form of a powder. More specifically, a powder form having an average particle diameter of 0.2 to 50 µm is preferable, and a powder form having an average particle diameter of 0.3 to 10 µm is more preferable. However, the particle shape is not particularly limited.

It is preferable that the soil treating agent of this invention contains the 2nd substance in the ratio of 10-300 weight part with respect to 100 weight part of 1st substances, and it is more preferable that it contains in the ratio of 50-100 weight part. If the ratio of the second substance is less than 10 parts by weight, the function of releasing hydrogen may be impaired by other substances, which may make it difficult to effectively remove dioxins in the soil. Conversely, when the proportion of the second substance exceeds 300 parts by weight, the proportion of the first substance in the soil treatment agent becomes small, so that it is difficult to effectively remove dioxins in the soil.

The soil treating agent of the present invention may contain a compound containing silicon, titanium, aluminum, calcium, and the like as impurities in addition to the above-mentioned first substance and second substance in a range that does not impair the desired effect thereof.

The soil treating agent of the present invention can be prepared by mixing the first substance and the second substance in the above-mentioned ratios and stirring sufficiently.

Referring to the soil treatment method of the present invention. This soil treatment method is a method for removing dioxins contained in the soil, and the soils to be treated are, for example, fly ash mixed soil, sludge, paddy soil, and field soil.

In the first aspect of the soil treatment method of the present invention, the above-described soil treatment agent is first added to the soil to be treated and mixed. At this time, it is preferable to set the mixing ratio of the soil treating agent to 1 to 50 parts by weight, and more preferably to 10 to 30 parts by weight with respect to 100 parts by weight of the soil. If the proportion of the soil treatment agent is less than 1 part by weight, it may be difficult to effectively remove dioxins contained in the soil. On the contrary, if it exceeds 50 parts by weight, there is a possibility that the first substance is excessively present in the treated soil, so that if the soil is used as agricultural soil, it may adversely affect plants and the like. In addition, the mixing ratio of the soil treating agent here is a ratio which converted the total amount of a 1st substance and a 2nd substance.

At this time, the amount of water in the mixture of the soil and the soil treatment agent is preferably set to 30 to 300% by weight of the total solids, more preferably 50 to 100% by weight. When this moisture content is less than 30 weight%, there exists a possibility that it may become difficult to remove dioxins in soil. On the contrary, when it exceeds 300% by weight, soil particles tend to settle in water, so that the contact rate between the soil particles and water is lowered, which may require a long period of time until dioxins in the soil are removed.

Then, the soil mixed with the soil treatment agent is left. In this case, the leaving period is preferably longer, but usually 7 days or more, preferably 10 days or more. In the case of less than 7 days, the dioxins contained in the soil may not be sufficiently removed from the soil.

In the second aspect of the soil treatment method of the present invention, the first substance and the second substance are added and mixed to the soil to be treated first. At this time, it is preferable to set the ratio of the first substance and the second substance in the same manner as the ratio in the above-described soil treatment agent. The total amount of the first substance to be added to the soil and the second substance is preferably set to 1 to 50 parts by weight, more preferably 10 to 30 parts by weight with respect to 100 parts by weight of the soil. When the ratio of the total amount is less than 1 part by weight, it may be difficult to effectively remove dioxins contained in the soil. On the contrary, if it exceeds 50 parts by weight, there is a possibility that the first substance is excessively present in the treated soil. Therefore, when the soil is used as agricultural soil, it may adversely affect plants and the like.

In this embodiment, the amount of water in the mixture containing the soil, the first substance and the second substance is preferably set to 30 to 300% by weight, more preferably 50 to 100% by weight of the total solids. When this moisture content is less than 30 weight%, there exists a possibility that it may become difficult to remove dioxins in soil. On the contrary, if it exceeds 300% by weight, the soil particles tend to settle in the water, so the contact rate between the soil particles and the water decreases, which may require a long time until the dioxins in the soil are removed.

In addition, the soil mixed with the first material and the second material is left. Here, it is preferable to set the leaving period similarly to the case of the 1st aspect mentioned above.

In the soil to which the soil treatment method of the present invention is applied, dioxin contained in the soil is effectively removed, and pH is maintained at neutral to acidity suitable for growing crops, and electrical conductivity is maintained at about 500 to 800 μS suitable for growing crops. Can be. Therefore, the treated soil, in particular, paddy or field soil, can be used as it is as a soil for cultivating crops even without further treatment. In addition, since the first material and the second material used in this treatment method are less likely to adversely affect the crop or the surrounding environment, the soil after the treatment is safe for the crop or the surrounding environment.

(Example)

Example 1

100 g of commercially available ferric trioxide (purity 95% or more) powder and 100 g of sodium hydrogen sulfite (reagent) powder were sufficiently mixed to obtain a soil treatment agent. Next, 100 g of the soil treatment agent was mixed with 300 g of paddy soil contaminated with dioxins, and 500 ml of water was further added and mixed. The paddy soil thus treated was left as it was, and the dioxins content (total amount of PCDDs, PCDFs and Co-PCBs), pH and electrical conductivity were examined after 1 day, 7 days and 14 days. Here, dioxins were investigated according to the method for measuring soil dioxins, as defined in the Soil Survey and Measurement Manual for Dioxins, which was enacted in 2000 by the Japan Environment Agency. In addition, pH was measured using the pH meter, and electrical conductivity was measured using the electrical conductivity meter. The results are shown in Table 1.

Dioxins content (pgTEQ / g per dry weight) Dioxin removal rate (%) pH Electrical Conductivity (μS) Before treatment 150 - 6.9 650 1 day later 100 33.3 6.3 750 7 days later 15 90.0 6.3 740 14 days later 13 91.3 6.4 745

Example 2

To 300 g of sludge contaminated with dioxins, 100 g of the soil treatment agent obtained in Example 1 was mixed, and 500 ml of water was further added and mixed. The sludge was left as it was, and in the case of Example 1, the dioxin content, pH and electrical conductivity of 1 day, 7 days and 14 days were similarly examined. The results are shown in Table 2.

Dioxins content (pgTEQ / g per dry weight) Dioxin removal rate (%) pH Electrical Conductivity (μS) Before treatment 1560 - 7.2 540 1 day later 480 69.2 6.3 580 7 days later 120 92.3 6.2 575 14 days later 130 91.7 6.2 580

Example 3

To 100 parts by weight of the sludge used in Example 2, the soil treating agent obtained in Example 1 was mixed at 10 parts by weight, 30 parts by weight and 50 parts by weight, respectively, and 200 ml of water was further added and mixed. This sludge was left as it was, and in the case of Example 1, the dioxins content after 7 days was investigated similarly. The results are shown in Table 3. According to Table 3, it can be seen that the dioxins contained in the sludge can be more effectively removed by increasing the soil treatment agent mixed in the sludge.

Soil treatment 0 parts by weight (one sludge) 10 parts by weight 30 parts by weight 50 parts by weight Dioxins content (pgTEQ / g dry weight) 1560 155 125 80 Dioxin removal rate (%) - 90.1 92.0 94.9

Since the soil treating agent of the present invention includes a first substance capable of releasing iron ions and a second substance capable of releasing hydrogen, dioxins contained in the soil can be effectively removed.

In the soil treatment method of the present invention, since the soil treatment agent of the present invention is added to the soil and mixed, or the first substance capable of releasing iron ions and the second substance capable of releasing hydrogen are added to the soil and mixed, respectively. Dioxins contained in the soil can be effectively removed.

Claims (11)

A first material capable of releasing iron ions, A soil treating agent comprising a second substance capable of releasing hydrogen. The soil treating agent according to claim 1, wherein the first substance is ferric trioxide (Fe ₂ O ₃ ). The soil treating agent according to claim 1 or 2, wherein the second substance is at least one of sodium hydrogen sulfite and sodium thiosulfate. The soil treating agent according to any one of claims 1 to 3, which contains 10 to 300 parts by weight of the second substance with respect to 100 parts by weight of the first substance. A soil treating method comprising the step of adding and mixing a soil treating agent containing a first substance capable of releasing iron ions and a second substance capable of releasing hydrogen to the soil. The soil treatment method according to claim 5, wherein 1 to 50 parts by weight of the soil treatment agent is added to and mixed with 100 parts by weight of the soil. The soil treatment method according to claim 5 or 6, wherein the amount of water in the mixture of the soil and the soil treatment agent is set to 30 to 300% by weight of the total solids of the mixture. And a process of adding and mixing the first substance capable of releasing iron ions and the second substance capable of releasing hydrogen, respectively, to the soil. The soil treatment method according to claim 8, wherein the first material and the second material are added to 100 parts by weight of the soil in a total amount of 1 to 50 parts by weight. The soil treatment method according to claim 8 or 9, wherein the ratio of the second substance to 100 parts by weight of the first substance is set to 10 to 300 parts by weight. The soil according to any one of claims 8 to 10, wherein the amount of water in the mixture containing the soil and the first substance and the second substance is set to 30 to 300% by weight of the total solids of the mixture. Treatment method.