(332h) Study of Foam Injection Technology for Soil Remediation Contaminated with Hydrocarbons

Soil flushing and soil washing are two remediation techniques preferred for cleaning soil contaminated with hydrocarbons due to their technical simplicity and cost. The efficiency of these techniques when injecting only water may be moderate due to the interaction of the contaminants with the soil components (organic, inorganic). The efficiency of soil flushing techniques may be increased with the use of surfactants. Surfactants decrease the interfacial tension between oil and water leading to the drag of contaminants in the flushing solution; also, they may interact with the soil surface, detaching the adsorbed hydrocarbon components by wettability exchange mechanisms.

The use of surfactants seem a good alternative to increase the efficiency of soil remediation processes, however, the injection of surfactant solutions may lead to different problems such as dragging of contaminant to clean sites even to water reservoirs causing secondary pollution. In the same line, surfactants adsorb to the minerals in the soil causing modification of the natural chemistry of the soil avoiding the natural recomposition of the system. Different strategies have been proposed: the implementation of surfactant solutions at low concentration, the use of bio-surfactants, and recently the injection of foams. Foams are colloid comprising on air trapped in a water matrix, this colloidal system can carry very low amount of surfactant in a very huge volume and possess a high viscosity, which can give control to the flooding process. In this work, we present a review on the latest technologies of foam injection for soil remediation, emphasizing the key variables to consider during soil flooding techniques. In the same line, we present the results we have obtained with a formulation comprising a mixture of synthetic surfactant (SDS) and a bio-surfactant in a test for removing hydrocarbons from soil, foam stability and its relation to hydrocarbon removal.