The effect of hydrophobic fine particles on the foam flushing remediation process

Abstract

Underground contamination with non-aqueous-phase liquids such as petroleum hydrocarbons is a major environmental problem. The organic phase immobilized by capillary trapping behaves as a continuing source of dissolved organic pollutants for the passing groundwater. Removal of these contaminants from the subsurface environment is essential to prevent the spreading of contamination. In situ foam flushing has proved to be an efficient process for non-aqueous-phase liquid soil remediation. Nevertheless, its efficiency can be affected by the surfactant’s adsorption on the soil matrix and also by the presence of fine particles. These particles may interfere with the foam breakage process and also with the surfactant solution foaming ability. The present work shows the effect of hydrophobic fine particles on surfactant foaming ability and foam stability. The impact of the adsorption of surfactant molecules on the surface of the hydrophobic particles was also determined. The results showed that the reduction in the foam stability, due to the presence of hydrophobic fine particles, was much higher than the reduction in the surfactant foaming ability. It was observed that the rate of film breakage due to the presence of hydrophobic micro-sized particles is to some extent higher than that of the hydrophobic nano-sized particles. It was also verified that the adsorption of surfactant molecules on the surface of the hydrophobic particles reduces their ability in breaking foams.

Acknowledgements: The authors wish to acknowledge Petróleo Brasileiro, CENPES/Petrobras, the Federal University of Rio de Janeiro, COPPE/UFRJ, the Engineering Research Center (ERC) for Particle Science and Technology at the University of Florida, the National Science Foundation (grant EEC-94-02989), and the industrial partners of the ERC for their support of this research.