JPS5888083A - Treatment of soil containing substance causing pollution - Google Patents

Abstract

PURPOSE:To completely eliminate the effluence of heavy metal substances causing pollution, by treating soil contg. the heavy metal substances with a pretreating agent, and then caking it with a caking agent comprising divalent metals, pref. magnesium oxide and a chloride. CONSTITUTION:To soil contg. heavy metal cations, 15% kaolinite, 3% slaked lime and 2% an addition agent having a hydroxyl group are added as a pretreating agent, to adsorb the heavy metal cations by oxygen atoms on the surface of kaolinite molecules. Thereafter, a caking agent comprising 50% magnesium oxide and 50% magnesium chloride is added to the pretreated soil to harden and cake the soil by the formation of oxichloride between the components of the caking agent. The caking reaction of the caking agent entails the extremely slight shrinkage of volume itself, so that there is no fear of the effluence of the heavy metal cations which would be caused by the formation of cracks after caking.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for treating soil and the like containing pollutants, such as those found in electrical fields, so that there is no risk of pollution occurring.

Conventionally, in order to dispose of soil containing one metal, such as cadmium or chromium, the soil containing these electric metals was mixed into cement and hardened by adding a hardening agent as necessary. However, this method cannot ensure complete processing.

That is, when treating soil containing hexavalent chromium, for example, conventionally the ±lIl is divided into a trench and subjected to a chemical reaction to reduce the hexavalent chromium to trivalent chromium, and then mixed into cement and solidified. However, in this case, we will take the trouble to prepare 3 in advance.
Chromium, which has been reduced to valence, is converted into 6 again by reaction in cement.
This is because, in addition to being easily oxidized to valent chromium, cement often shrinks and cracks occur during solidification, and when cracks occur, the chromium oxidized to hexavalent chromium may flow out from there. Therefore, in the past, the highly treated soil had to be transported to an appropriate location and disposed of, and at the same time it was necessary to backfill with new, safe soil, resulting in a large expense burden.

In view of the above-mentioned prior art, the inventor of the present invention has conducted extensive research on a method for treating soil containing pollutants that can completely eliminate the outflow of pollutants after solidification. , the present invention has been completed, and the method of the present invention, when treating ±1 containing polluting substances such as heavy metals, pre-treats with a pre-treatment agent that is most compatible with the polluting substances, and then pre-treats with a divalent metal Preferably, it is characterized by being solidified by a solidifying agent comprising an oxide and a chloride of magnesium.

That is, the present invention can be used to completely treat soil containing pollutants such as metals, etc. l-1 It is pretreated with a pretreatment agent that is most compatible with the pollutants contained in it, such as linmetiae, and as an assimilation agent, it is replaced with the conventionally used cement. It is preferable to use magnesium oxide and chloride, mix them with the pretreated soil, and utilize the hardening reaction that occurs between the magnesium oxide and chloride. The idea is to completely suppress the outflow of pollutants such as 1-metal slag after solidification.

Next, examples of the present invention will be described.

l) The pollutants contained in the soil to be treated are kaolinite 15% slaked lime (○a(QH)t) 3s Additive that supports hydroxyl groups 2% Solidifying agent magnesilla oxide A (Mgo) 50% magnesium chloride ( MgC4) 30% and kaolinite,
The kaolinite molecules in the pretreatment agent consisting of slaked lime and an additive that has M hydroxyl groups have a double layer structure in which a layer of aluminum octahedrons is sandwiched by a layer of silicon tetrahedrons, and the kaolinite molecules are Since no other tetrahedral layer is laminated in the layer, hydroxide ions (OH-) derived from other components in the pretreatment agent are coordinated to the octahedral layer, and the hydroxyl ions and Hydrogen bonds are formed between other kaolinite molecules present above the octahedral layer and oxygen atoms in the silicon tetrahedral layer, and the adjacent kaolinite molecular layers are strongly connected.

Therefore, when soil etc. containing heavy metal cations is pretreated with the above pretreatment agent, the Togane cations are converted into protons (H is absorbed by the released oxygen atoms, in other words, the oxygen atoms present on the surface of kaolinite molecules.If this pretreated soil is mixed with a solidifying agent consisting of magnesium oxide and magnesium chloride, the components of the solidifying agent It is solidified by a reaction in which oxychloride is produced between the two and hardened.

Therefore, while the kaolinite molecules attract heavy metal cations to their surfaces, the molecular layers are strongly connected by hydrogen bonds, and moisture and the heavy metal cations cannot enter between the eyebrows of these molecules. Therefore, the degree of expansion and contraction is small, and furthermore, the shrinkage rate of the reaction material itself in which the assimilate solidifies is extremely small, so cracks occur after solidification.
There is no risk of the heavy metal cations leaking out.

If the heavy metal iodine is hexavalent chromium, it may be reduced to trivalent chromium before being treated by the method of the present invention, but sodium thiobisulfate may be used as an additive in the pretreatment agent. This is preferable because it is possible to omit the reduction operation at the same time as solidification, and there is no fear that trivalent chromium will be oxidized to hexavalent chromium after solidification.

Father, when treating soil containing cations as mentioned above, the pretreatment agent is sufficient as long as it attracts the skeleton cations and attaches them to the surface, so it is not necessary to use isomorphic substitution of aluminum and magnesium ions.・Thus, it may be a partially negatively charged silicate clay, a calho, etc. that forms cells with a negative charge, and in the latter case, the strength of the cation attraction is as follows: Soil IIf# Various species in the solution 2) When the pollutant contained in the ±1 to be treated is a heavy metal anion: For example, the pretreatment agent may include Gibusai) (ju(OH)a)
It is sufficient to use one that includes the following.

That is, gibbsite (u(on), Hydroxyl ions on the surface are protonated to create positively charged sites, which attract 1 gold and 1 anion, making the soil to be treated more attractive (
After pretreating a-6(OH)a) with a pretreatment agent containing rubber,
It is sufficient if it is mixed with an assimilating agent having the same components as in the above case and solidified.

Soil containing cadmium, a heavy metal as a pollutant, was solidified into a block using the method of the present invention, and the block was immersed in water and the concentration of cadmium ions flowing out was fixed by atomic absorption spectrometry. No cadmium ions were detected.

As the present invention is as described above, it is suitable as a method for treating soil containing pollutants such as heavy metals.

Claims (1)

[Claims] 1. When treating soil containing pollutants such as heavy metals,
After pretreatment with a pretreatment agent most compatible with the pollutant,
A method for treating soil, etc. containing pollutants characterized by solidifying with a solidifying agent consisting of an oxide and a chloride of a divalent metal, preferably magnesium. 2. A method according to claim 1, comprising a compound and kaolinite. 3. The method according to claim 194, wherein the processing agent forms micelles carrying negative charges. 4. The method according to claim 1, in which the pretreatment agent is protonated to carry a positive charge. 5. Claim 1, in which the solidifying agent comprises magnesium oxide and magnesium chloride. to the method described in item 4.