Evaluation of surfactants/cosolvents for desorption/solubilization of Phenanthrene in clayey soils

Abstract

Throughout the USA, numerous sites exist where the soils have been contaminated by polycyclic aromatic hydrocarbons (PAHs). These compounds may be toxic, mutagenic and/or carcinogenic, so these sites threaten human health and the environment and prompt remediation is warranted. In situ flushing with surfactants/cosolvents has shown promise for treating PAH‐contaminated soils that are uniform and possess a high permeability, but the efficiency of this process is severely limited when heterogeneous and/or low permeability soils are present. For these difficult situations, electrokinetically enhanced in situ flushing offers great potential, but this method is highly dependent on the type of purging agent that is used. Thus, in this laboratory investigation, batch desorption experiments were conducted to evaluate different surfactants/cosolvent solutions for use in electrokinetically enhanced in situ flushing. The surfactants/cosolvents were evaluated on their ability to desorb and solubilize phenanthrene, a representative PAH, from two widely varying clayey soil types. The soils were artificially contaminated at four PAH concentrations, and batch tests were conducted using six different surfactant/cosolvent solutions. The results indicated that phenanthrene was more strongly bound to the soil with the higher organic content, and the surfactants with a higher hydrophile – lipophile balance number (HLB) caused greater PAH desorption and solubilization. Furthermore, the surfactant solutions performed better when they were used at a higher concentration. Compared to the cosolvent solution or a combined mixture of the cosolvent and surfactant solutions, greater desorption and solubilization of the contaminant occurred when the surfactant solution was used by itself.