Treatment of a complex emulsion of a surfactant with chlorinated organic compounds from lindane wastes under alkaline conditions by air stripping

Abstract

Surfactant-enhanced aquifer remediation is commonly applied in polluted sites with dense non-aqueous phase liquids(DNAPLs). This technique transfers the contamination from subsoil to an extracted emulsion, which requires further treatment.This work investigated the treatment of a complex emulsion composed of a nonionic surfactant and real DNAPL formed ofchlorinated organic compounds (COCs) and generated as a lindane production waste by air stripping under alkaline conditions. Theinfluence of the surfactant (1.5−15 g·L−1), COC concentrations (2.3−46.9 mmol·L−1), and temperature (30−60 °C) on the COCvolatilization was studied and modeled in terms of an apparent constant of Henry at pH > 12. In addition, the surfactant stability wasstudied as a function of temperature (20−60 °C) and surfactant (2−10 g·L−1), COC (0−70.3 mmol·L−1), and NaOH (0−4 g·L−1)concentrations. A kinetic model was successfully proposed to explain the loss of surfactant capacity (SCL). The results showed thatalkali and temperature caused the SCL by hydrolysis of the surfactant molecule. The increasing surfactant concentration decreasedthe COC volatility, whereas the temperature improved the COC volatilization. Finally, the volatilization of COCs in alkalineemulsions by air stripping (3 L·h−1) was performed to evaluate the treatment of an emulsion composed of the COCs (17.6 mmol·kg−1) and surfactant (3.5 and 7 g·L−1). The air stripping was successfully applied to remove COCs (>90%), reaching an SCL of 80%at 60 °C after 8 h. Volatilization can remove COCs from emulsions and break them, enhancing their further disposal.