Equilibrium partitioning of a non-ionic surfactant and pentachlorophenol between water and a non-aqueous phase liquid

The partitioning of the non-ionic surfactant Tergitol NP-10 (TNP10) and pentachlorophenol (PCP) into a mineral oil light nonaqueous phase liquid (NAPL) were quantified in batch tests. Due to the ionizable nature of PCP, the effects of pH and ionic strength ()mu)) on the equilibrium partitioning were evaluated. NAPL:water partition coefficients (Kn:w) of TNP10 ranged from 3 to 7 Lwater/LNAPL. Enhanced PCP dissolution into water from the NAPL was achieved at aqueous TNP10 concentrations >= 200 mg/L. Surfactant addition of 1200 mg/L TNP10 increased the aqueous PCP concentrations by 14-fold at pH 5 versus 2 to 3-fold at pH 7 as compared to PCP aqueous solubility. The more significant response at the lower pH is likely due to the greater hydrophobicity of PCP at the lower pH, which is approaching PCPʹs pKa of 4.7. Higher ionic strength ((mu) 0.11 versus 0.001 M) increased Kn:w of PCP by 10–33% without surfactant, compared to a more than 150% increase with a dose of 4000 mg/L TNP10. This work contributes information relevant to the application of surfactants to remediate sites contaminated with NAPLs.