PCE solubilization and mobilization by commercial humic acid

In this paper, comparison is made of terms describing solubilization of hyd rophobic organic compounds (HOC) by dissolved humic substances (DHS) and co mmercial non-ionic surfactants. This paper examines the ability of a commer cial humic acid (Aldrich humic acid) to solubilize and mobilize tetrachloro thene (PCE) residual in porous media. The constant for solubilization of PC E by Aldrich humic acid is shown to be a factor of two to thirty times less than that published for dodecyl alcohol ethoxylate surfactants, showing th at Aldrich humic acid is less capable than some non-ionic surfactants at so lubilizing residual PCE. The depression of PCE-water interfacial tension in the presence of DHS is shown to be significantly less than published value s for a non-ionic surfactant, and surfactant mixtures, indicating that the DHS used in this study is less prone to cause mobilization of non-aqueous p hase liquids relative to surfactants. Several possible advantages of DHS us e in the remediation of subsurface media contaminated with HOC are describe d, including the ability of DHS to solubilize HOC irrespective of the DHS c oncentration, and potential lesser tendency of DHS to depress the interfaci al tension between non-aqueous phases and water relative to surfactants (an advantage when mobilization is undesired). (C) 1999 Elsevier Science B.V. All rights reserved.