JP2009011956A - Method for insolubilizing heavy metal and the like in contaminated soil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for insolubilizing soil contaminated with a heavy metal and the like that can stably preserve the soil during long-term storage and transportation by preventing the soil from contacting air and water or being effected by sulfuric acid ions and the like contained in underground water. <P>SOLUTION: Contaminated soil is added or mixed with a basic substance composed of 80% of a magnesium component, 10% of a calcium component, 3.5% of a silicon component, 3% of sulfur component and 1.5% of aluminum to obtain pretreated soil for insolubilization. The soil contaminated with a heavy metal and the like is stably insolubilized by adding or mixing the pretreated soil for insolubilization with a sulfate of iron or manganese. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for insolubilizing soil contaminated with heavy metals and the like.

Conventional methods for treating soil contaminated with heavy metals include “Survey / Countermeasure Guidelines and Operation Standards Concerning Soil / Groundwater Contamination” (January 1999) and “Soil Contamination Countermeasures Law” (established in May 2002). (1) A method of solidifying physicochemically by mixing a solidifying agent such as cement with soil.
(2) There is a method of chemically insolubilizing by mixing insolubilized chemicals in soil.
In order to solve problems attracted by soil contaminated with heavy metals, transportation of contaminated soil to the final disposal site, chemical treatment with chemicals, physicochemical solidification with concrete, etc. are adopted. Has been.

And since such a biofilm efficiently processes the organic matter in the wastewater, the BOD volumetric load is about five times that of the activated sludge method, which is an extremely efficient wastewater treatment method. However, the biofilm treatment method was originally an advantageous treatment method for drainage with a low BOD and a large amount of water, and was used for tertiary treatment. However, in recent years, it has begun to be used for primary processing and secondary processing, focusing on the high BOD volumetric load. In addition, a rotating contact aeration method, an anaerobic immersion filter bed, a sprinkling water filter bed, and the like are also processing methods with a high BOD volume load.
JP 2004-66183 A

  When such conventional concrete is added and mixed and solidified, amphoteric ions (for example, lead) that chemically change into both anions and cations are eluted, and heavy metals such as fluorine are eluted. There was a problem that it could not be insolubilized.

  The present invention solves such a conventional problem, and is not affected by sulfate ions or the like that come into contact with air or water during long-term storage or transportation, or contained in underground groundwater. An object of the present invention is to provide a method for insolubilizing soil contaminated with heavy metals that can be stably stored.

  Note that heavy metals and the like defined here refer to lead, arsenic, chromium, cadmium, boron, and fluorine.

  In order to achieve the above object, the method for insolubilizing heavy metals and the like in contaminated soil of the present invention has a magnesium component 80%, calcium component 10%, silicon component 3.5%, sulfur component 3%, aluminum 1. A basic substance mixed with 5% is added or mixed to form insolubilized pretreated soil, and then iron or manganese sulfate is added to or mixed with the insolubilized pretreated soil.

  According to the present invention, heavy metals contained in contaminated soil can be stably insolubilized.

  The invention according to claim 1 is a method for insolubilizing contaminated soil contaminated with heavy metals, etc., wherein the contaminated soil has a magnesium component of 80%, a calcium component of 10%, a silicon component of 3.5%, and a sulfur component of 3%. In addition, a basic substance mixed with 1.5% aluminum is added or mixed to form insolubilized pretreated soil, and then iron or manganese sulfate is added to or mixed with the insolubilized pretreated soil. is there.

  Thereby, the pH value of the insolubilized soil can be stabilized by the magnesium component (magnesium hydroxide) and the sulfate constituting the basic substance, and can be stably insolubilized without elution of heavy metals or the like. .

  In addition, the calcium component and sulfate react to produce calcium sulfate, so that the insolubilized pretreated soil can be solidified, which leads to ground strengthening when backfilling into the ground.

  The invention according to claim 2 is a method for insolubilizing contaminated soil contaminated with heavy metals, etc., and adding or mixing a basic substance mixed with 75% sulfur component and 23% aluminum component to the contaminated soil. In addition, after the insolubilized pretreated soil is obtained, iron or manganese sulfate is added to or mixed with the insolubilized pretreated soil.

  As a result, the aluminum component (aluminum hydroxide) constituting the basic substance and sulfate can form aluminum sulfate and stabilize the pH value of the insolubilized soil. Can be insolubilized.

  The invention according to claim 3 is a method for insolubilizing contaminated soil contaminated with heavy metals and the like, wherein the contaminated soil is mixed with 35% calcium component, 30% sulfur component and 30% iron component. A substance is added or mixed to form insolubilized pretreated soil, and then iron or manganese sulfate is added to or mixed with the insolubilized pretreated soil.

  As a result, the calcium component (calcium hydroxide) constituting the basic substance and the sulfate can form calcium sulfate and form an iron compound, thereby realizing buffering of the pH value of the insolubilized soil. It can be stably insolubilized without elution.

  Embodiments of the present invention will be described.

  After adjusting the moisture content of contaminated soil contaminated with fluorine from 15% to 20%, mixed with 80% magnesium, 10% calcium, 3.5% silicon, 3% sulfur and 1.5% aluminum After adding the basic substance, stirring and mixing to make insolubilized pretreated soil, iron or manganese sulfate was mixed, stirred and left for 1 day, then the pH of the liquid contained in this soil was measured, and this liquid The elution concentrations of fluorine and fluorine compounds from the above were measured by the method defined in JIS (JIS K0102).

  The initial pH of contaminated soil contaminated with fluorine was 7.6, and the amount of fluorine elution from groundwater was 2.3 mg / L. After that, in the test solution mixed with iron or manganese sulfate, stirred and allowed to stand for 1 day, the pH is 9.2 and the fluorine elution amount is 0.0015 mg / L. It turns out to be stable.

  In addition, after adjusting the moisture content of the contaminated soil contaminated with fluorine from 15% to 20%, a basic substance mixed with 75% sulfur component and 23% aluminum component is added or a basic substance mixed is added and stirred. After mixing and making insolubilized pretreated soil, iron or manganese sulfate is mixed, stirred and left for 1 day, then the pH of the liquid contained in this soil is measured, and elution of fluorine and fluorine compounds from this liquid The concentration was measured by a method defined in JIS (JIS K0102).

  The initial pH of contaminated soil contaminated with fluorine was 7.6, and the amount of fluorine elution from groundwater was 2.3 mg / L. After that, in the test solution mixed with iron or manganese sulfate, stirred and allowed to stand for 1 day, the pH is 9.4 and the fluorine elution amount is 0.0012 mg / L. It turns out to be stable.

  In addition, after adjusting the moisture content of the contaminated soil contaminated with fluorine from 15% to 20%, a basic substance mixed with 35% calcium component, 30% sulfur component and 30% iron component is added, mixed with stirring, After making insolubilized pretreated soil, iron or manganese sulfate was mixed in the insolubilized pretreated soil, stirred and allowed to stand for 1 day, then the pH of the liquid contained in this soil was measured, and fluorine and The elution concentration of the fluorine compound was measured by a method defined in JIS (JIS K0102).

  The initial pH of contaminated soil contaminated with fluorine was 7.6, and the amount of fluorine elution from groundwater was 2.3 mg / L. After that, in the test solution in which iron or manganese sulfate was mixed, stirred and allowed to stand for 1 day, the pH was 10.4 and the fluorine elution amount was 0.0016 mg / L. It turns out to be stable.

  In this way, by adding and mixing basic substances and further mixing and stirring sulfates, heavy metals and the like contained in the soil can be stabilized as minerals under alkaline conditions.

  The method for insolubilizing heavy metals here is about excavating soil contaminated with heavy metals, adding and mixing basic substances on the ground, and mixing and stirring sulfates. When the soil is surface layer, it can be mixed with a stabilizer that is a heavy construction machine or a backhoe, and the deep layer part of the soil can be mixed with powder of basic substance and sulfate, It is also possible to use a power blender that is injected in a slurry state.

  If the site to be cleaned is wide, a mixing method using a belt conveyor may be used. Conversely, if the site to be cleaned is narrow, mixing may be performed using trommel.

Claims (3)

A method for insolubilizing contaminated soil contaminated with heavy metals, etc., in which 80% magnesium component, 10% calcium component, 3.5% silicon component, 3% sulfur component and 1.5% aluminum were mixed in the contaminated soil. A method for insolubilizing heavy metals or the like in contaminated soil, comprising adding or mixing a basic substance to form insolubilized pretreated soil, and then adding or mixing iron or manganese sulfate to the insolubilized pretreated soil. A method of insolubilizing contaminated soil contaminated with heavy metals, etc., comprising adding or mixing a basic substance mixed with 75% sulfur component and 23% aluminum component to the contaminated soil to obtain insolubilized pretreated soil, Alternatively, a method for insolubilizing heavy metals or the like in contaminated soil, comprising adding or mixing manganese sulfate to the insolubilized pretreated soil. A method for insolubilizing contaminated soil contaminated with heavy metals, etc., comprising adding or mixing a basic substance mixed with 35% calcium component, 30% sulfur component and 30% iron component to the contaminated soil, and insolubilizing pretreated soil Then, a method for insolubilizing heavy metals or the like in contaminated soil, comprising adding or mixing iron or manganese sulfate to the insolubilized pretreated soil.