Remediation of Heavy Metals Polluted Soil Using Metal Insolubilizing Materials

Abstract

Heavy metal ions, one kind of harmful substance, may exist in the soil irrelevant to artificial development, and soil contamination, due to soil and rock containing these naturally derived heavy metals, has recently become apparent. Thus, in an amendment that came into effect in 2010 of Japan, the scope of countermeasures and regulations for contaminated soil was amended to "contaminated soil derived from artificial development" and "naturally derived contaminated soil". When naturally derived contaminated soil is encountered during the carrying out of construction work, countermeasures against this type of soil contamination are necessary. In this research, new metal-insolubilizing materials are developed in order to improve the insolubilization treatment which is one method for treating contaminated soil. Specifically, tests are conducted to clarify the insolubilization effect on heavy metals, and the insolubilization mechanism is chemically and mineralogically discussed.

Mineral Materials as a Neutralizing Agent Used on Soil Contaminated with Copper

“…The durability of these bonds depends on the soil pH, amount and type of minerals, redox potential, sorption capacity and organic matter content [7,27]. A method that allows reduction of the harmfulness of heavy metals is the addition of neutralizing materials to the soil [3,[28][29][30] so as to bind metals in insoluble metal-mineral or organo-metallic forms, which-under favorable conditions-may remain in the soil in harmless forms for a long period [9,31]. The most common neutralizing materials are zeolites, bentonite, clay, lime, and also organic materials, like compost, tree bark, farmyard manure and peat [3,23,30].…”

“…The most common neutralizing materials are zeolites, bentonite, clay, lime, and also organic materials, like compost, tree bark, farmyard manure and peat [3,23,30]. Until recently, the methods of heavy metal immobilization have been the only available and feasible form of reclamation of contaminated soils, allowing the restoration of biological life and plant cover in degraded areas [29,32]. High concentrations of heavy metals in soil result in higher than natural concentrations in plants, which may result in an increased flow of metals to further links in the trophic chain [12,33], where they may accumulate and their harmful effects may be long-term.…”

Zeolite Properties, Methods of Synthesis, and Selected Applications

“…Zeolite remediation of contaminated soils reduces the amount of phytoavailable forms of trace elements, leading to the restoration of soil homeostasis [ 120 , 121 ]. When mixed with Portland cement, zeolites are an effective stabilizing agent and, in the case of trace elements, an immobilizing agent [ 122 ].…”