Evaluation of naphthenic acids as a soil remediation agent: A physicochemical perspective

Removal of residual oil from reject sand grains is a major challenge in solvent-based bitumen extraction. A proposed solution is to wash the oil-contaminated sand grains with water and surfactants (the remediation agent). Due to the very favourable interfacial properties of naphthenic acids, namely, its ability to significantly reduce the oil–water interfacial tension and render the solid substrate hydrophilic, the surfactant has been proposed as a promising remediation agent. In this study, we evaluated the washing performance of naphthenic acids and demonstrated its inadequacy in sand remediation. The fundamental reason for the surfactant’s poor performance was the inadvertent formation of a bicontinuous microemulsion which consumed much of the naphthenic acids, leaving little if any for remediation purposes.