The mechanism of the surfactant-aided soil washing system for hydrophobic and partial hydrophobic organics.

A surfactant-aided soil washing mechanism is proposed in this study by examining nine common organic contaminants, which were divided into two groups, hydrophobic compounds and partial hydrophobic compounds, depending on the respective soil partitioning of contaminants, K(oc). The presence of a free non-aqueous phase liquid in the soil washing system is critical to determine the soil washing performance curves. A mathematical model is proposed to describe soil-washing performance at various surfactant concentrations. The resulting slopes and intercepts from the model for the performance prediction are linearly related to K(oc). In addition, a transition zone between the hydrophobic and partial hydrophobic compounds was observed, and has been used in verifying the proposed mechanism successfully by overdosing and underdosing the contaminants in the system.