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About Insolubilization

Summary of Insolubilization

Insolubilization is a technology to control elution of heavy metals from soil or rocks to stabilize geochemically using minerals.

Requisites of Insolubilization

At KANKYO ZAIRYO ENGINEERING, we are developing insoluble material and absorbent under the following concept.

  • The mineral directly react to heavy metals and the mechanism of action is clear.
  • Use of mineral whose cause and effect is valid under natural condition (Natural Purification)
  • The method is stable and safe under natural condition
  • Being extremely irreversible in adsorption and sorption character under the use condition

Mechanism of Isolubilization

At Kankyo Zairyo, we mainly use crystallization effect and mineral adsorption for isolubilization phenomenon.

Use of Crystallization Effect

In crystallization effect, heavy metal is isolubilized with use of reaction of the minerals of adsorption property by adding a constituent element with an adsorption property. Because the isolubilization encourages the formation of adsorption mineral, the material component factor is customized based on the composition of the pollutant in subject.

Hydrotalcite Mg6Al2(CO3)(OH) 16 4H2O

Hydrotalcite has the crystal structure of layers made of magnesium and aluminum alloy. The negative ion between these layers is exchangeable; they are exchanged due to the difference in the electric charge of the material originally in the layers and heavy metal in subject.

Figure - Schematic diagram of hydrotalcite and Intercalation

Hydrotalcite is confirmed to be stable at pH=4 ~13@300 degrees Celsius.

Use of Mineral Adsorption

In the mineral adsorption method, heavy metals are adopted into a mineral by adding a material that is standardized as adsorption mineral in its chemical characteristics and physical property. In order to maximize the function of mineral adsorption, we monitor the detail of the environment of the subject and offer an effective controlling of the subject environment upon necessity.

Schwertmannite Fe8O8(OH)8-2X(SO4)X nH2O(1≦x≦1.75)

Schwertmannite in realm of nature has a tunnel-like structure in which sulfate ion is coordinated in iron. By the ligand exchange with Sulfate ion,it adsorbs maximum of 4~8wt% of it own weight of arsenic. Schwertmannite is an iron mineral of low crystallinity, and a metastable mineral of cyrstalline iron mineral goethite. When it adsorbs arsenic, its solubility becomes lower and its structure is stabilized.

Figure - Schematic Diagram of Schwertmannite

Tunnel-like Structured Iron Mineral

When naturally accumulated schwertmannite in geo-stratum is age determined with radiocarbon dating, it was confirmed that schwertmannie has been stable for over 18,000 years.