JP2002355665A - Method for cleaning soil containing cadmium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently clean a soil containing cadmium. SOLUTION: This method for cleaning the soil polluted with cadmium is characterized in that the water soluble salt of a metal selected from sodium, potassium, magnesium and calcium, an ammonium salt and one or more kinds selected from water-soluble lower carboxylic acids are applied to the soil containing cadmium, and that plants having an absorption power for cadmium are planted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for purifying cadmium-containing soil with plants.

[0002]

2. Description of the Related Art A soil covering method and a soil removal method are generally used for purifying cadmium-containing soil. However, the earth covering method only prevents the diffusion of the top soil of the cadmium-containing soil, and the earth removal method only moves the soil, and is not a fundamental solution.

[0003] As a technique for containing cadmium-containing soil, insolubilization with a solidifying agent or vitrification and insolubilization by applying a high voltage have been developed. However, the soil subjected to the containment treatment changes its properties greatly and cannot withstand secondary use. In addition, cadmium is simply insolubilized and cannot be said to be a fundamental purification, and the cost in the latter case is enormous.

Further, as a method of fundamentally removing and removing cadmium from cadmium-containing soil, a washing method and a purification method by heating and vaporizing have been developed and are being implemented. However, in this case, excavation and movement of the soil are involved. It was difficult to obtain public recognition of this, and the cost was enormous.

On the other hand, it is conceivable to apply environmental purification using plants, that is, so-called phytoremediation, to purification of cadmium-containing soil in response to such chemical or physical techniques. According to this method, cadmium can be purified in situ by harvesting and removing cadmium-enriched plants, and it can be treated at lower cost compared to other technologies, and significantly changes the properties of the soil after treatment. Can be purified without the need.

[0006] Such phytoremediation is effective in preventing harmful substance elution and diffusion by absorbing and fixing harmful substances eluted from soil by roots, even if plants enriched with harmful substances are not harvested and removed, Because of its ability to cover harmful substances containing harmful substances, that is, the effect of preventing the diffusion of harmful substances due to wind and rain, and the ability to improve the landscape by greening, it has attracted attention as a revolutionary purification method for soil containing harmful substances.

However, cadmium present in soil is generally strongly adsorbed to soil constituents.
The absorption of cadmium by plants is slow, and there is a problem that it takes a long time to purify by simply applying a conventional plant purification method as it is, and it is not possible to purify to a predetermined standard within a certain period.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for purifying cadmium-containing soil efficiently and reliably in a short time by phytoremediation.

[0009]

Means for Solving the Problems In view of the above circumstances, the present inventors have conducted various studies on the cadmium existence form in a cadmium-containing soil, and as a result, applied a water-soluble salt of a specific metal or the like to the cadmium absorption capacity. By planting a plant having, without any adverse effect on the growth of the plant,
The inventors have found that the cadmium absorption efficiency of the plant is dramatically improved, and the cadmium purification effect is significantly improved, and the present invention has been completed.

That is, the present invention relates to a method for purifying cadmium-contaminated soil, which comprises adding a water-soluble salt, an ammonium salt and a water-soluble lower carboxylic acid of a metal selected from sodium, potassium, magnesium and calcium to a cadmium-containing soil. The present invention provides a method for purifying cadmium-containing soil, characterized by applying one or more kinds selected from the group consisting of: and planting a plant having cadmium absorption ability.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Cadmium-containing soil to be purified according to the present invention includes soil containing urban cadmium elemental units, compounds or ions in urban areas, forests, factory sites, agricultural lands, swamps, and the like. For example, 1991
Soil in which the amount of cadmium eluted exceeds the soil environmental standard as measured by the method specified in Notification No. 46 of the Environment Agency, and soil containing 2 mg or more of cadmium in 1 kg of soil per kg.

On agricultural land, the Ministry of Agriculture and Forestry Ordinance No. 47
Cadmium content of rice, wheat, soybeans, peanuts, leafy vegetables is 0.2 mg or more per kg, and that of other vegetables is 0.05 mg or more, as measured by the method specified in item (1) or the equivalent measurement method. It can be suitably applied.

In the present invention, one or more selected from water-soluble salts, ammonium salts and water-soluble lower carboxylic acids of metals selected from sodium, potassium, magnesium and calcium are applied to improve the cadmium absorption capacity. The plant is planted, but by adding such a substance, cadmium which has been insolubilized and adsorbed in the soil can be solubilized in any case, and the cadmium absorption efficiency of the plant is dramatically improved.

The water-soluble salt of a metal selected from the group consisting of sodium, potassium, magnesium and calcium is a salt obtained from a hydroxide and an acid of the metal.
A substance having a dissolution weight (g) of 1 or more dissolved in 00 mL of pure water may be a hydrate or a solvate as well as an unsolvate. Examples of such metal water-soluble salts include sodium chloride, sodium iodide, sodium iodate, sodium oxide, sodium hydroxide, sodium sulfide, sodium sulfate, sodium hydrogen sulfate, sodium nitrate, sodium carbonate, sodium silicate, and boric acid. Sodium, sodium formate, sodium acetate, sodium oxalate, potassium chloride, potassium iodide, potassium iodate, potassium oxide, potassium hydroxide, potassium sulfide, potassium sulfate, potassium hydrogen sulfate, potassium nitrate,
Potassium carbonate, potassium silicate, potassium borate, potassium acetate, potassium oxalate, magnesium chloride, magnesium iodide, magnesium sulfide, magnesium sulfate, magnesium nitrate, magnesium carbonate, magnesium silicate, magnesium acetate, calcium chloride, calcium iodide Metal chlorides such as calcium chloride, magnesium chloride, sodium chloride, and potassium chloride are preferable, and calcium chloride is particularly preferable from the viewpoint of secondary contamination, price, and effect.

Examples of the ammonium salt include ammonium sulfate, ammonium acetate, ammonium chloride, ammonium nitrate, ammonium sulfide and the like, with ammonium sulfate being particularly preferred.

The water-soluble lower carboxylic acids include, for example, organic carboxylic acids having 2 to 6 carbon atoms, and specific examples thereof include citric acid, acetic acid, tartaric acid, lactic acid, butyric acid, malic acid, itaconic acid, succinic acid and gluconic acid. Acids, propionic acid and the like, and succinic acid and lactic acid are particularly preferable.

In the present invention, one or more of these metal water-soluble salts, ammonium salts and water-soluble lower carboxylic acids can be used in combination, and particularly when two or more are used in combination. Preferably, calcium chloride and succinic acid are used.

In the present invention, an aminocarboxylic acid may be used together with the metal water-soluble salt, ammonium salt or water-soluble lower carboxylic acid. Particularly, a combination of a water-soluble metal salt and an aminocarboxylic acid may be used. Is preferred. The aminocarboxylic acid used here forms a complex with a metal cation. For example, amino acids such as alanine, glutamic acid, glycine, and cysteine, ethylenediaminetetraacetic acid (EDTA), and ethylene glycol bis (2-aminoethyl ether) Acetic acid (E
GTA), 1,2-diaminocyclohexanetetraacetic acid (D
CTA), diethylenetriaminepentaacetic acid (DTPA),
2-hydroxyethylethylenediamine triacetic acid (HED
TA), nitrilotriacetic acid (NTA) and the like. In particular, it is preferable to use a combination of calcium chloride and EDTA.

The metal water-soluble salt, ammonium salt or water-soluble lower carboxylic acid and aminocarboxylic acid may be applied directly to a cadmium-containing soil. This is particularly effective in terms of uniformity. In this case, the concentration of the metal water-soluble salt, ammonium salt, water-soluble lower carboxylic acid or aminocarboxylic acid in the aqueous solution is preferably 0.1 to 30% by weight, particularly preferably 1 to 10% by weight. Metallic water-soluble salts, ammonium salts or water-soluble lower carboxylic acids and aminocarboxylic acids can be used as a mixture thereof.

The application time of the metal water-soluble salt, ammonium salt or water-soluble lower carboxylic acid and aminocarboxylic acid is not particularly limited.
During germination or emergence, the plant may be in any growth period, but the applied metal water-soluble salt, ammonium salt, water-soluble lower carboxylate, aminocarboxylic acid or solubilized cadmium is not absorbed by the plant and diffuses. In order to prevent this, it is particularly preferable to apply the composition after the sowing or planting of the plant has become vigorous.

The application rate is not particularly limited as long as it can solubilize cadmium insolubilized and adsorbed in the soil and does not hinder the growth of the plant. cadmium-containing soil 1m ² per 0.0
It is preferable to spray 1 to 2 kg, preferably 0.1 to 1 kg, because it can reduce the phytotoxicity to plants. Spraying can be performed several times within this range, or a combination of two or more of water-soluble metal salts, ammonium salts, and water-soluble lower carboxylic acids can be applied.

The plant used in the purification method of the present invention may be any plant having a cadmium absorbing ability, and of course, a plant which is considered to have a low cadmium absorbing ability under the conditions of the present invention. Plants that exhibit good cadmium absorption capacity when planted can also be used.

The plants that can be used in the present invention include:
For example, Malvaceae, Acalyptaceae, Rubiaceae, Rubiaceae, Akebiaceae, Brassicaceae, Iridaceae, Isopine family, Poaceae,
Inomotosouaceae, Zinniaeaceae, Ukogiaceae, Urabiaceae,
Osidaceae, Ossilylaceae, Oleoptera, Oxalidae, Cattails, Cyperaceae, Cannaceae, Fennelaceae,
Asteraceae, Lepidoptera, Apocynaceae, Ranunculaceae, Papilionidae, Lumbidae, Gummiaceae, Mulberry family, Poppyceae, Scrophulariaceae, Araceae, Asteraceae,
Lingaceae, Lamiaceae, Lymphalidae, Gingeraceae, Ginsengaceae, Honeysuckleaceae, Purslaneaceae, Violaceae, Aceraceae, Spiraceae, Polygonaceae, Tatamidae, Boxwood, Azaleaaceae, Camellia, Emberaceae, Nephridae , Craneaceae, Euphorbiaceae, Rhododendronaceae, Passifloridae, Toberiaceae, Solanaceae, Nadesicidae, Euonymus, Rhododendronaceae, Nosenharenaceae, Hempericaceae, Hanashinobidae, Rosaceae, Amaryllidaceae, Cypressaceae, Convolvulaceae, Butterfly Family, Anthracidae, Anthracidae, Buddleia, Grapeaceae, Crassinaceae, Papilionaceae, Pinaceae, Leguminosae, Dipterocarpaceae, Purple cormorant, Laceae, Magnoliaaceae, Magnoliaaceae, Ilexaceae, Salixaceae,
Examples include plants belonging to the family Astridaceae, Saxifragaceae, Brackenaceae, and Lily.

[0024] Above all, Akazidae, Brassicaceae, Gramineae, Asteraceae, Mulberry family, Apiaceae family, Polygonaceae family, Papilionidae family, Rosaceae family,
Leguminosae, a plant belonging to the willow family is preferred, and specifically, Akazaceae Akaza, Shiroza, Hamaakaza, Fudanso,
Sugar beet, Butterfly, Salicornia japonica, Okahijiki, Spinach, Matsuna, Brassicaceae, Miyazuna, Yamazuna, Arabidopsis, Hatazao, Niwahatazao, Niitakahatazao, Suzushiroso, Yamahatazao, Samurai, Samurai, Samurai, Samurai Undiabrana, Turnip, Nozawana, Kyona, Komatsuna, Kisaragina, Pozai, Japanese mustard, Chilemenkarasina, Takana, Zasai, Japanese mustard, Swedish cub, Hakuran, Kale, Habotan, Broccoli,
Cauliflower, cabbage, cabbage, kohlrabi, amazuna, juniper, konronsou, smelt, hamana, hanahatazao, takanazuna, ezoinu-zuna, inu-nazuna, kibanasuzushiro, kibana-araiseto, suzuna-sama, suzuna-sena, suzuna-suna Araceite, Dutch agaricus, Giant agaricaceae, Japanese radish, Radishes radishes, Inugarashi, Skasitagobo, Shirogarashi, Hatazaogarashi, Gumbinazuna, Kikalashi; Grassesaceae Shiba, Wheat, Camoigusa, Konukagusa, Yamanukabo, Osuzume, Japanese wildflowers Oats, oats oats, oats, kazunokogusa, kobansou,
Himekobansou, Suzumeokahiki, Hydrangea, Ohigeshiba, Juzudama, Adlay, Pampasgrass, Bermudagrass, Orchardgrass, Meechishiba, Inubiye, Tainubiye, Indohiye, Hie, Shikokubie, Ohishiba, Weeping Lovegrass, Kazekusa, Kogomeka-kosehate Narcovier, Teosinto, Tall Fescue, Meadow Fescue, Sheep Fescue, Red Fescue, Koubou, Barley, Chigaya, Italian Ryegrass, Perennial Ryegrass, Dokumugi, Susuki, Hachijousski, Caryas, African Rice, Rice, Millet, Lepidoptera, Bahiakomesu, Suzume Sparrow fir, Chikarashiba, pearl millet, napier grass, acne, lead canary grass, canary grass, scallop, Mossy, Reed, Tsuruyoshi, Seitakayoshi, Suzumeokatabira, Kentucky Bluegrass, Itachigaya, Hiedari, Sugarcane, Chiksha, Rye, Enokorogosa, Akienokorogosa, Awa, Hanaokorogosa, Sorghum, Megarukaya, Wheatbush, Cornflower Grass, Sudangrass; Asteraceae Yarrow, Roman Chamomile, Burdock, Hagoromogy, Scarlet Artemisia, Kawamurayomigi, Taragon, Astor, Daisies,
Sengakusa, Tsurugamagusa, American ginkgo, Himecosmos, Alearia thistle, Tokasen, Calendula, Ezogiku, Finfish thistle, Chabo thistle, Japanese tobacco, Safflower, Cornflower, Chrysanthemum, Chrysanthemum, Chrysanthemum, Chrysanthemum, Chicory, Thistle
Cosmos, Artichokes, Dimorfoseca, Teningiku, Ooteningoku, Hawkweeder, Sunflower, Jerusalem artichoke, Butterfly, Seika Awadachisou, Canadian goldenrod, Akinokirinsou, Himejion, Stevia, Dandelion, Himakosuma, Hamakosuma, Hamaguru Shimaguwa, Yamaguwa; Apiaceae caraway, cumin, carrot, Ookyo, Fennel, Chidumegusa, Seri; Polygonaceae buckwheat, Ibukitranoo, Sakuratade, Yanagitade, Sanaetadae, Oinutade, Inutade, Otaketake, Oitatake, Oitake, Oitake, Oitake Rhinoceros, Rhododendron officinalis, Sorrel, Rumex; Rubiaceae, Pterodactyla, L., L., Carnation, Sekichiku, Hime Deshiko, Fujinadeshiko, Tatsutanadeshiko, Kawaranadeshiko, Gypsophila, Gypsophila paniculata, Sennow, Tsumekusa, Hakobe, Halinadesico; , Yamahagi, marbahagi, nishikihagi, miyaginohagi, miyakogusa, lupine, kidney bean, peas, kuzu, sendai hagi, alpine clover, strawberry clover, sashikusou, red clover, white clover, radino clover, sub clover, fava bean, sage beetle Sesbania, crimson clover, alfalfa; willows, weeping willow, red willow, river willow, pussy willow, fox , Oobayanagi and the like are preferable. Above all, crested rape, rape, sorghum, tall fescue, Seika kawadachisou, knotweed, tatsumanadeshiko, red clover, red eye willow, giant fennel, yamabuki, sudan grass, orchard grass, perennial ryegrass, bahiagrass, sespania, guineagras, especially cornflower preferable. The plant used is not limited to one kind, and for example, two or more kinds of different families may be planted simultaneously.

The method of planting a plant in the present invention can be carried out by any method such as sowing seeds, planting seedlings, and transplanting grown plants, depending on the plant. Cultivation of the plant may be performed by a usual method, and fertilization, irrigation, spraying of herbicides and other chemicals may be performed as necessary. In addition, when the plant is collected and treated, or when annual grass is used, or when the degree of contamination is severe, it is preferable to repeat the method of the present invention.

After the cultivation, the plant may be harvested by a usual method. For example, only the above-ground portion may be cut off or pulled out from the root, but it is preferable to pull out and collect it from the root. Then, the collected plant is subjected to an appropriate treatment as a cadmium-containing substance.

[0027]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1 Akadama clay and peat moss were mixed in a volume ratio of 8: 2, and 5 g / L of a composite control fertilizer High Control (manufactured by Asahi Kasei Kogyo) was further mixed as a slow-release fertilizer. An aqueous solution of cadmium nitrate (Kanto Chemical Co., Ltd., reagent grade 1) was added thereto and mixed with stirring so that the cadmium mass per dry soil was 25 mg / kg, to prepare a cadmium-containing soil. The cadmium content of this cadmium-containing soil after preparation is 40 mg.
/ Kg.

When the prepared cadmium-containing soil is 1 area in size,
/ 2000 are filled into Wagner pots, 3 g of sorghum seeds were sown, and normal cultivation management such as watering was performed as appropriate.

Two months after sowing, sorghum has grown to 50 cm or more, where calcium chloride, magnesium chloride, sodium chloride, potassium chloride, and ammonium sulfate were added as soil additive substances as calcium, magnesium, sodium, potassium, and ammonium, respectively. 1000 mL of the solution prepared to be 0.35 M was applied to the strain base. This was applied once a month during the cultivation period, for a total of four times.

After cultivation for 7 months, the plant is removed from the Wagner pot by removing it, and the soil is stirred and mixed, air-dried and collected, the soil is decomposed with perchloric acid, and the residue is removed by filtration to obtain. The cadmium content was measured by measuring the resulting solution by an atomic absorption method. Table 1 shows the results.

COMPARATIVE EXAMPLE 1 Calcium sulfate was applied as a soil additive substance.
The same operation as described above was performed. The results are shown in Table 1.

Comparative Example 2 The same operation as in Example 1 was performed without applying the soil additive. The results are shown in Table 1.

Comparative Example 3 The same operation as in Example 1 was carried out without cultivating sorghum and without applying any soil additives. The results are shown in Table 1.

[0035]

[Table 1]

Example 2 In an experimental system similar to that of Example 1, citric acid, acetic acid, tartaric acid, lactic acid, malic acid, itaconic acid, succinic acid, and gluconic acid were each prepared as a soil-adding substance at a concentration of 15 g / L. 1000 mL of the solution was applied to the stock. This was applied once a month during the cultivation period, for a total of four times.

After cultivation for 7 months, the cadmium content in the soil was measured in the same manner as in Example 1. Table 2 shows the results.

Comparative Examples 4 and 5 are the same as Comparative Examples 2 and 3, respectively. Table 2 shows the results.

[0039]

[Table 2]

Example 3 The same cadmium-containing soil and cultivation container as in Example 1 were used.
The plants shown in Table 3 were grown. Two months after sowing, 1000 mL of a 0.35 M calcium chloride aqueous solution was sprayed on each, and the spraying was applied once a month during the cultivation period, four times in total. After cultivation for 7 months, the cadmium content in the soil was measured by the same treatment as in Example 1. Table 3 shows the results.

Comparative Example 6 Primrose was grown according to the experimental method of Example 3, and
Cadmium content in the soil was measured by the same treatment as described above. Table 3 shows the results.

Comparative Example 7 Cadmium content in soil was measured in the same manner as in Example 1 except that the plant was not cultivated in the same manner as in Example 1, except that no plant was cultivated. Table 3 shows the results.

[0043]

[Table 3]

Example 4 Cadmium-contaminated soil (cadmium content: 5.6 mg / kg)
Was filled into a Wagner pot having a size of 1/2000 ares, 3 g of sorghum seeds were sown, and ordinary cultivation management such as watering was performed as appropriate.

Three months after sowing, the sorghum has grown to 1 m or more. Therefore, the compound shown in Table 4 as a soil-added substance and 1000 mL of a solution prepared so as to have a concentration were applied to the strain base. This was applied once a month during the cultivation period, for a total of three times.

After cultivation for 7 months (four months after the start of application), the cadmium content in the soil was measured by the same treatment as in Example 1. Table 4 shows the results.

Comparative Example 8 The same operation as in Example 4 was performed without applying the soil additive. The results are shown in Table 4.

Comparative Example 9 The same operation as in Example 4 was performed without cultivating sorghum and without applying any soil additive. The results are shown in Table 4.

[0049]

[Table 4]

[0050]

According to the method of the present invention, cadmium-containing soil can be efficiently and reliably purified, and the properties of land and soil are not impaired. In particular, the method is effective for reuse as agricultural land. is there.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Uchiyama 2-4-2 Daisaku, Sakura City, Chiba Prefecture Inside the Central Research Institute of Pacific Cement Co., Ltd. (72) Inventor Naoko Tanaka 2-4-2 Daisaku, Sakura City, Chiba Prefecture Taiheiyo Cement Co., Ltd. Central Research Laboratory F-term (reference) 2B022 AA01 AB20 BA02 BB01 4D004 AA41 AB03 AC07 CA17 CC11 CC15 CC20 DA03 DA10

Claims (8)

[Claims] 1. A method for purifying cadmium-contaminated soil, wherein the cadmium-containing soil is selected from a water-soluble salt, an ammonium salt and a water-soluble lower carboxylic acid of a metal selected from sodium, potassium, magnesium and calcium. A method for purifying cadmium-containing soil, comprising applying one or more kinds of plants and planting a plant having a cadmium absorption ability. 2. A water-soluble salt, ammonium salt or water-soluble lower carboxylic acid of a metal selected from sodium, potassium, magnesium and calcium is added to a cadmium-containing soil in an area of 1 m ^2.
The purification method according to claim 1, wherein the amount is 0.01 to 2 kg per application. 3. The purification method according to claim 1, wherein the metal water-soluble salt is a metal chloride selected from sodium chloride, potassium chloride, magnesium chloride and calcium chloride. 4. The method according to claim 1, wherein the water-soluble metal salt is calcium chloride. 5. The water-soluble lower carboxylic acid according to claim 1, wherein the water-soluble lower carboxylic acid is selected from citric acid, acetic acid, tartaric acid, lactic acid, butyric acid, malic acid, itaconic acid, succinic acid, gluconic acid and propionic acid. Purification method. 6. The method according to claim 1, further comprising applying an aminocarboxylic acid to the cadmium-containing soil. 7. A plant having the ability to absorb cadmium is selected from the group consisting of Akazaceae, Brassicaceae, Gramineae, Asteraceae, Mulberry, Apiaceae,
The purification method according to any one of claims 1 to 6, wherein the purification method is selected from plants belonging to the Polygonaceae family, the Polygonaceae family, the Rosaceae family, the Legume family, and the Salix family. 8. The plant having the ability to absorb cadmium includes buffalo, oilseed rape, sorghum, tall fescue, scorpionfish, knotweed, tatsumanadesiko, red clover, red willow, willow oak, yamabuki, sudan grass, orchard grass, peranial ryegrass, bahiagrass The purification method according to any one of claims 1 to 6, wherein the purification method is selected from the group consisting of cepa, sespania, guineagrass, corn, and crotalaria.