HEAVY METAL FIXATION/STABILIZATION IN SOILS

The microenfractionator® is capable of up to 95% homogeneity of the soil mixed.

The treatment of heavy metal contaminated soil is a major concern of the environmental community. Heavy metals can leach out of impacted soils into surface or ground water, eventually entering the food chain. Depending on which heavy metal contaminant(s) are involved, serious public health concerns and/or environmental impact can result due to exposure to the contaminants. Health concerns include but are not limited to neurological damage, cancer, reproductive interference, and birth defects.

Heavy metal contaminants can be complexed with other chemicals to reduce their solubility and restrict their migration throughout the environment. Several methods of heavy metal fixation/stabilization processes are available. One of the methods of stabilization is mixing the soil with portland cement. This method can be very effective in the prevention of contaminant leaching, but it can significantly increase the volume of soil post treatment. The addition of fly ash to the soil is another option to stabilize the leachability of certain heavy metals. Again, a significant increase in soil volume can occur when fly ash is used as a stabilization agent. In addition, the mechanism that both of these technologies use to prevent heavy metal leachability is elevating the pH of the soil. Most heavy metals are not leachable at high pH. There are exceptions to this rule. The leachability of some heavy metals can actually increase at higher pH levels. Knowledge of the leaching characteristics of the heavy metal(s) being treated is essential. In some cases, a combination of heavy metal contaminants will be present in a given soil. The combination of metal contaminants may not be compatible for a specific treatment because of the variability of leachability with regard to soil pH.

A new method of soil treatment for soils impacted with heavy metals is now available. This method uses relatively low percentages of added material to achieve low contaminant leachability. This method uses a combination of chemicals to react with the metal contaminant in the soil to form metal-salt complexes. These complexes are very water insoluble, and very stable under a variety of pH and other environmental conditions. This method of treatment does not significantly increase the soil volume.

Any of the above treatment methods have useful applications. All of the above technologies require superior soil homogenization to work properly. The H&H Microenfractionator® is capable of up to 95% homogeneity of the soil mixed. The key to any fixation/stabilization process is excellent soil mixing. The way any of these systems works is direct contact between the chemical contaminant and the added chemical reagent(s). Without effective mixing, none of these processes will be effective.