Surfactant-Enhanced Solubilization of Chlorinated Organic Compounds Contained in DNAPL from Lindane Waste: Effect of Surfactant Type and pH

Abstract

Application of surfactants in the remediation of polluted sites with dense nonaqueous phase liquid (DNAPL) still requires knowledge of partitioning between surfactants and pollutants in the organic and aqueous phases and the time necessary to reach this balance. Two real DNAPLs, generated as wastes in the lindane production and taken from the polluted sites from Sabiñanigo (Spain), were used for investigating the solubilization of 28 chlorinated organic compounds (COCs) applying aqueous surfactant solutions of three nonionic surfactants (E-Mulse® 3 (E3), Tween®80 (T80), and a mixture of Tween®80-Span®80 (TS80)) and an anionic surfactant (sodium dodecyl sulfate (SDS)). The initial concentrations of surfactants were tested within the range of 3–17 g·L−1. The pH was also modified from 7 to >12. The uptake of nonionic surfactants into the organic phase was higher than the anionic surfactants. Solubilization of COCs with the nonionic surfactants showed similar molar solubilization ratios (MSR = 4.33 mmolCOCs·g−1surf), higher than SDS (MSR = 0.70 mmolCOCs·g−1SDS). Furthermore, under strong alkaline conditions, the MSR value of the nonionic surfactants was unchanged, and the MSR of SDS value increased (MSR = 1.32 mmolCOCs·g−1SDS). The nonionic surfactants did not produce preferential solubilization of COCs; meanwhile, SDS preferentially dissolved the more polar compounds in DNAPL. The time required to reach phase equilibrium was between 24 and 48 h, and this contact time should be assured to optimize the effect of the surfactant injected on COC solubilization.

Non-Ionic Surfactant Recovery in Surfactant Enhancement Aquifer Remediation Effluent with Chlorobenzenes by Semivolatile Chlorinated Organic Compounds Volatilization

“…The surfactant selected to carry out the experiments was E-Mulse 3 ® (E3) (EthicalChem), which is a non-ionic surfactant with a critical micelle concentration (CMC), measured of . This surfactant has been successfully applied in the solubilization of 28 different chlorinated organic compounds present in a real dense non-aqueous phase liquid (DNAPL) to the aqueous phase, including CB and DCBs [ 26 ].…”

“…In the last case, the aqueous phase was saturated with the mixture of VCOCs, adding the corresponding amount of SVCOCs to obtain a saturated emulsion of organic phase in the aqueous surfactant emulsion. The amount of VCOCs added was calculated from the molar solubilization ratio MSR (amount of SVCOCs that can be solubilized in the surfactant solution when saturation is reached) obtained elsewhere for a complex mixture of chlorinated compounds in this surfactant [ 26 ] (MSR = ). The emulsions were agitated during 4 h and left to settle 24 h without agitation, checking the total solubilization of VCOCs added.…”

Treatment of a Complex Emulsion of a Surfactant with Chlorinated Organic Compounds from Lindane Wastes under Alkaline Conditions by Air Stripping

“…E3 was selected because it is a biodegradable and non-toxic surfactant 11 and has been successfully applied in the solubilization of COCs from DNAPL-R to the aqueous phase. 31 The air employed to perform the experiments was supplied by Carburos Metaĺicos, with a quality of 99.999% (Alphagaz 1 AR, Air Liquid). The aqueous solutions were prepared with high-purity water from a Millipore Direct-Q system with resistivity >18 mΩ•cm at 25 °C.…”

“…In the last case, a certain amount of DNAPL-S was added to the aqueous phase with the surfactant (2−10 g•L −1 ) to obtain a stable emulsion. The moles of solubilized organic compounds per mole of the surfactant in micellar solution was the molar solubilization ratio (MSR) for DNAPL-R or DNAPL-S in E3, as determined elsewhere 31 and resulting in 4.33 mmol COCs•g surf −1 . The emulsions were agitated for 4 h and left to settle for 24 h without agitation; after this time, the concentration of COCs in the emulsion was stable over time, and the amount of COCs was measured.…”

Synthetic and Natural Surfactants for Potential Application in Mobilization of Organic Contaminants: Characterization and Batch Study

“…Surfactants are amphiphilic organic molecules, typically with a hydrophobic tail group and a hydrophilic head group [15]. They can concentrate at the interface between two immiscible phases, orienting the hydrophobic group toward the organic phase and the hydrophilic group toward the aqueous phase, resulting in a decrease in the interfacial tension (IFT) between the phases [16].…”