Effect of soil type on electrokinetic removal of phenanthrene using surfactants and cosolvents

Numerous sites have been contaminated with polycyclic aromatic hydrocarbons (PAHs), and these sites pose a significant risk to public health and the environment because PAHs are often toxic, mutagenic, and/or carcinogenic. Furthermore, these sites are often difficult or costly to remediate because PAHs are hydrophobic and highly resistant to degradation. The in situ flushing process using surfactants and/or cosolvents has shown great promise for sites possessing uniform and high-permeability soils, but it is generally ineffective for sites containing heterogeneous and/or low-permeability soils. Thus, for difficult soil conditions, electrokinetics can be integrated with the in situ flushing process to improve soil-solution-contaminant interaction. This investigation was conducted to evaluate the effects of two different low-permeability soils, kaolin and glacial till, on electrokinetically enhanced flushing. Each soil type was used in three bench-scale electrokinetic experiments, where each test employed a different flushing solution, deionized water, a surfactant, or a cosolvent. The results indicated that the contaminant was more strongly bound to the glacial till than the kaolin, and this was attributed to its higher-organic content. The glacial till also generated a greater electrical current and electro-osmotic flow, and this was probably a result of its higher-carbonate content and more diverse mineralogy. Based on the contaminant mass remaining in the soil, it was apparent that the surfactant or cosolvent solution caused contaminant desorption, solubilization, and/or migration in both soils, but additional research is required to improve PAH removal efficiency.