Using tracer technique to study the flow behavior of surfactant foam.

Surfactant foam was used to remove absorbed hydrocarbons from soils. The nature and extent of the foam pathway decide the efficiency of this technology. The characteristics and behavior of foam flow are difficult to visually observe. In this study, laboratory sandbox experiments were performed to estimate the flow behavior of surfactant foam and thus elucidate the properties and flow behavior of surfactant foam. To quantitatively determine the distribution of foam and evaluate accurately the flow field of foam in the soil, this study designed a special technique, applying micro-scale iron powder as a tracer. The foam generated with 4% (w/v) mixed solution of Span 60 and sodium dodecyl sulfate (SDS) showed an excellent stability and quality, which made it particularly apt for this study. The results indicated that the foam flows through the zone above the clay planes and also flows through the zone between the clay planes. The heterogeneous sand does not inhibit the invasion of foam flow. Moreover, the results of tracer tests and photographs of the foam distributions in sandbox were identical in the behavior of foam flow. This knowledge is valuable for providing insight into the foam remediation of contaminated soil.