Behavior of DNAPL mixture of organometallic and chlorinated solvent in the presence of surfactants and alcohols as density modifying agents

Abstract

This work evaluates the behavior of surfactant and alcohols in combination with a mixture of tributyltinchloride (TBT) and tetrachloroethylene (PCE) with the goal of modifying the mixed oil from being a dense non-aqueous phase liquid (DNAPL) to a light non-aqueous phase liquid (LNAPL). Phase behavior of the mixed oil was studied under various combinations of surfactant, alcohol, and salinity. Phase density conversion was examined using pseudo-ternary phase diagrams constructed between the mixed oil, surfactant solution (4 wt%), and two types of alcohols (n-butyl alcohol (BuOH) and tert-butyl alcohol (TBA)). Aqueous phase solubilization and oil phase density modification were studied at varying alcohol to surfactant (A/S) ratios. The results showed that the optimum surfactant system was sodium dihexylsulfosuccinate (SDHS) and hexadecyl diphenyloxidedisulfonate (C16DPDS) (3.6 wt% and 0.4 wt%, respectively) with salt (NaCl) of 3 wt%. From pseudo-ternary phase diagrams, BuOH was found to produce a larger LNAPL region than TBA. From solubilization studies, the surfactant system plus either TBA or BuOH caused PCE preferential solubilization and this preference was more pronounced at higher total surfactant concentration in the system with TBA addition. In terms of density modification, BuOH produced lower oil density than TBA at high A/S ratio. This phase behavior knowledge can be used to optimize site remediation of organometallic DNAPLs.

Keywords:

• Neutral buoyancy
• microemulsion
• organometal
• TBT
• EACN

Acknowledgment

This study was funded by DuPont Chemical Co., Centre of Excellence on Hazardous Substance Management (HSM), University of Oklahoma Institute for Applied Surfactant Research and WaTER Centers, and the Graduate School at Chulalongkorn University. While DuPont's financial support is gratefully acknowledged, DuPont endorsement of data/research conclusions is not implied. The authors also would like to thank Dr. Seelawut Damrongsiri for his valuable comments.