USE OF CATIONIC SURFACTANTS TO MODIFY SOIL SURFACES TO PROMOTE SORPTION AND RETARD MIGRATION OF HYDROPHOBIC ORGANIC-COMPOUNDS

Cationic surfactants can be used to modify surfaces of soils and subsurface materials to promote adsorption of hydrophobic organic compounds (HOC). Batch and column experiments were performed to investigate this phenomenon with the cationic surfactant dodecylpyridinium (DP), a series of chlorobenzenes as representative HOC, and a low organic carbon aquifer material (Lula). The adsorption isotherm of DP was highly nonlinear; at micromolar concentrations, DP was adsorbed strongly but not irreversibly; at millimolar concentrations, adsorption was relatively weak. Distribution ratios of the chlorobenzenes varied nonlinearly with DP loading. The elution of chlorobenzenes from columns packed with DP-treated aquifer material was examined; a transport model based on the results of the batch experiments and the local equilibrium assumption yielded an acceptable approximation for the coelution of DP and HOC from the column. It is concluded that treatment of surfaces with cationic surfactants shows promise as a means of promoting HOC sorption in a variety of treatment processes.