Sustainable application of surfactants in soil remediation: Selective pollutants adsorption and hydrogen peroxide-driven adsorbent regeneration

Abstract

The uncontrolled disposal of the liquid lindane wastes have led to the formation of dense non-aqueous phase liquids (DNAPL), consisting of 28 chlorinated organic compounds (COCs), contaminating soil and groundwater. Surfactant-enhanced aquifer remediation is proposed as technology to treat these sites. However, the polluted emulsion generated must be manged on-site. In this work a two-step process is applied to treat emulsion composed of E-Mulse® 3 (4 g·L−1) as surfactant and a DNAPL (2 gCOCs·L−1). In the first, the COCs were selectively adsorbed in a granular activated carbon (GAC) column with Fe (II) previously adsorbed (10–20mg·g-1) onto the carbon surface, recovering an aqueous phase with surfactant for their reuse. In the second step, the spent GAC was regenerated with a 40 g·L−1 solution of hydrogen peroxide fed to the column at 2 mL·min−1 to promote the oxidation of the COCs adsorbed in the GAC. The kinetic and adsorption model in a multisolute (surfactant and DNAPL) system has been proposed. Five successive cycles of regeneration/adsorption have been successfully applied in the column process. About 50 % of the COCs were retained from the emulsion, and more than 70 % of the surfactant was recovered. The consumption of unproductive oxidants decreased with the number of regeneration cycles. The water effluent obtained after regeneration of GAC did not present chlorinated compounds desorbed and nontoxic by-products generated, such as short-chain acids.