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

Raúl García-Cervilla,David Lorenzo,Arturo Romero,Aurora Santos

doi:10.3390/ijerph17124494

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.

Highlights

Contamination of soil and groundwater by organic compounds from industrial activities has become a major environmental problem [1]
The mass of organic phase not dissolved at equilibrium conditionsEQ was obtained from the dense nonaqueous phase liquids (DNAPL) mass balance, as shown in equation (S1) to (S3) in the Supplementary Information
The partition behavior of the four surfactants is similar for each DNAPL, and the differences found can be due to experimental error

Summary

Introduction

Contamination of soil and groundwater by organic compounds from industrial activities has become a major environmental problem [1]. This contamination is often due to the accidental release or intentional dumping of hydrophobic organic liquid phases into the environment, resulting in a separate liquid phase, referred to as nonaqueous phase liquids (or NAPLs), that persists in the subsurface [2]. Other chlorinated organic pollutants forming DNAPLs include pesticides and chlorinated compounds used for their synthesis [5,6,7] Most of these DNAPLs are persistent in the environment due to their hydrophobic nature and low biodegradability, characterized by high toxicity and bioaccumulation and, Int. J. Public Health 2020, 17, 4494; doi:10.3390/ijerph17124494 www.mdpi.com/journal/ijerph

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Conclusion