Water Research 37 (2003) 4663–4672 Aqueous chemistry and interactive effects on non-ionic surfactant and pentachlorophenol sorption to soil Sung-Kil Park a , Angela R. Bielefeldt b, * a POSCO, Environment and Energy Department, 1 Goedong-dong, Nam-gu, Pohang, Gyeongbuk 790-785, P.O. Box 36, Pohang, South Korea b Department of Civil, Environmental and Architectural Engineering, University of Colorado, Boulder, Campus Box 428, Boulder, CO 80309-0428, USA Received 23 January 2003; received in revised form 5 June 2003; accepted 1 August 2003 Abstract Non-ionic surfactant addition was investigated as a method to remediate pentachlorophenol (PCP) contaminated soil. The goal was to quantify surfactant (Tergitol NP-10 (TNP10)) and PCP sorption to soil and their interactive effects under varying pH, ionic strength, and soil conditions. Up to 16,700 mg/kg of TNP10 partitioned to soil, with increasing sorption far above the critical micelle concentration (CMC) and with greater amounts of PCP present. Approximately 40–45 times more TNP10 and 20–30 times more PCP sorbed to the finer soil with higher organic matter content. Aqueous TNP10 concentrations well above the CMC (X5500 mg/L) were required to enhance PCP desorption from the soil. As pH increased by 0.5–0.85 units, TNP10 sorption decreased by 14–25% and PCP sorption as measured by the log of the equilibrium partition coefficient decreased by 1–1.5. A lower ionic strength of 0.03 versus 0.112 M increased PCP desorption from contaminated soil by 5–17% in the presence of TNP10. This work is relevant to designing ex situ soil washing or surfactant-aided PCP remediation. r 2003 Elsevier Ltd. All rights reserved. Keywords: Pentachlorophenol; Non-ionic surfactant; Soil sorption 1. Introduction Many toxic organic contaminants sorb strongly to soil, making remediation at these contaminated sites more difficult. Lab and field-scale studies have demon- strated that surface-active agents (surfactants) have the potential to increase the desorption of contaminants (pesticides, polyaromatic hydrocarbons (PAHs), and chlorinated solvents) from soil due to enhanced solubi- lity [1–3]. In addition, 10 pilot-scale and two full-scale field tests have demonstrated that surfactant-enhanced aquifer remediation coupled with pump-and-treat tech- nologies may enhance the clean up of contaminated sites [4]. Pentachlorophenol (PCP) is a widespread soil and groundwater contaminant due to extensive use for wood preservation and other pesticide applications [5]. Soil samples from highly contaminated sites have contained up to 13,200 mg PCP/kg soil [6]. The soil sorption of PCP is influenced by the fraction of organic carbon in the soil (f oc ), cation exchange capacity, soil texture, specific surface area, and liquid characteristics [7–10]. Schellenberg et al. [10] showed that regardless of soil type, at the same pH (7.5), ionic strength (mp0:003 M), and temperature (20  C) the organic carbon partition coefficient (K oc ) of non-ionized PCP derived from linear isotherms remained fairly constant at approximately 3  10 4 mL/g. The soil:water partition coefficient, K p was equal to f oc K oc . ARTICLE IN PRESS *Corresponding author. Tel.: +1-303-492-8433; fax: +1- 303-492-7317. E-mail address: Angela.Bielefeldt@Colorado.edu (A.R. Bielefeldt). 0043-1354/$ - see front matter r 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.watres.2003.08.005