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KANKYO ZAIRYO ENGINEERING Co., Ltd.

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Summary of SPEX Series

SPEX Series heavy metal adsorption mechanism

SPEX series generate mineral using the constituent of calcium or aluminum contained in the subject mineral during the insolubilization process,and adopt the heavy metal into the mineral generated.
In conventional "Surface Adsorption" method, heavy metal is electrically pulled to the surface of the mineral; this method has the weakness in being easily seceded depending on the surrounding environment.
In adsorption mechanism of SPEX series, on the other hand, heavy metal is adopted into the mineral using the effect of exchange of structural ion of the mineral and the heavy metal ion, creating strong bonding (chemical adsorption) to let heavy metal held on with relative stability compared to the surface adsorption.

Figure : Schematic Diagram of Adsorption Mechanism of Heavy Metal

Insoluble Material: When SPEX series is mixed with contaminated soil, it starts to react with water in the soil. (It may become necessary to control pH of the surrounding environment and may need appropriate watering.) As a result of the reaction of the material constituent and calcium or aluminum, layered clay mineral is generated.
In the layered clay mineral, lead or cadmium is exchanged with calcium constituent (Intercalation), arsenic and fluorine are exchanged with other substances, and then held in as part of the mineral constituents.


Applicability

SPEX series may be applied to the following various cases. If the subject case is not included in below figure, it may be pre-tested for applicability.



Long Term Stability of SPEX Series

Long Term Stability of SPEX Series (Acid / Alkali Added Test)

In propagation of insolubilization method, an establishment of a test to provide evidence of the long term stability of the purifier and stableness of the treated soil was essential.
Acid / Alkali Added Test is a testing method to withstand these needs; it is a test method adopted by Geo-Environmental Protection Center.

Acid/alkali added test is a testing method to simulate 100 years worth of natural condition by provision of acid from acid rain water and alkali condition from concrete to the soil on treatment, and then to verify that the isolubilization effect is stable on long term basis. pH is controlled to accord with No.18 Ministry of Environment Notice when adding the acid rain over exposed soil, and concrete for alkali effect to assume the test.

Test with assumption of approx. 100 years of exposing with acid raid (Acid added test)

With assumption of pH4.0 of acid rain water at 2,000mm per annum of precipitation, the acid volume of 1 square meter over 100 years is calculated at 7.69mmol/kg.
Acid water of this volume is sprayed to accord with the No. 18 Ministry of Environment Notice to perform the test.

Test with assumption of soil being exposed to concrete (Alkali added test)

This is a case in which concrete is assumed to be buried underground. Alkali volume in effluent (solvent) is [OH-]=7.69meq/L(pH 11.9). Using the equivalent volume of solvent, the test is performed to accord with the No. 18 Ministry of Environment Notice.


SPEX-A


SPEX-M

SPEX Series have been proven in the long term stability evaluation test to have sufficient insolubilization effect.